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NX.   STATE   UNIVERSITY     D.H,   HILL   LIBRARY 


S00275674  V 


This  book  is  due  on  the  date  indicated 
below  and  is  subject  to  an  overdue  fine 
as  posted  at  the  Circulation  Desk. 


AMERICAN  SCIENCE  SERIES 


ESSENTIALS  OF 

COLLEGE  BOTANY 


BY 

CHAELES  E.  BESSEY,  Ph.  D.,  LL.  D. 

HEAD   PROFESSOR   OP  BOTANY    IN    THE     UNIVERSITY   OF   NEBRASKA 

AND 

ERNST  A.  BESSEY,  Ph.  D. 

PROFESSOR   OP  BOTANY   IN   THE   MICHIGAN   AGRICULTURAL.  COLLEGE 


EIGHTH    EDITION    OF    "tHE    ESSENTIALS    OF   BOTANY' 
ENTIRELY    REWRITTEN 

With  206  Diagrammatic  Illustrations 

rJ .  0.  UOLLEiJS  OF  A.  &  1 


,^:\^ 
t 


NEW  YORK 
HENRY  HOLT  AND  COMPANY 


COPYRIGUT,    1914 
BY 

HENRY  HOLT  AND  COMPANY 


THE . MAPLE . PRESS • TOBK • PA 


PREFACE 

In  offering  this  ])ook  to  college  teachers  it  may  not  be 
amiss  to  refer  to  the  great  change  that  has  taken  place 
in  the  teaching  of  Botany  in  America  since  the  prepara- 
tion of  its  predecessor  thirty-five  years  ago.  Then 
botanical  laboratories  were  just  coming  into  existence, 
and  for  the  first  time  students  of  Botany  were  able 
to  study  protoplasm  and  cells  and  tissues  and  other 
minute  structures  of  plants.  It  is  a  matter  of  history 
that  half  a  dozen  years  later  the  publisher's  objection 
to  the  caption  '' Laboratory  Studies"  for  a  new  edition, 
was  able  to  bring  about  the  substitution  of  ''Practical 
Studies,"  as  less  likely  to  prejudice  teachers  against  such 
presentation  of  the  subject.  Looking  back  to  that  time 
we  realize  what  progress  has  been  made  in  the  teaching 
of  the  science,  for  to-day  every  college  has  its  laboratory  for 
the  study  of  plant  structure,  and  this  change  in  teaching 
has  gone  so  far  that  it  has  invaded  the  secondary  schools, 
in  which  there  are  now  many  well-equipped  botanical 
laboratories. 

Looking  at  the  science  from  another  standpoint  it  is 
of  interest  to  note  that  thirty-five  years  ago  the  number 
of  species  of  known  plants  was  between  125,000  and 
150,000,  while  to-day  it  has  risen  to  more  than  233,000. 
Then  the  number  of  flowering  plants  was  placed  at  a 
little  more  than  100,000,  while  now  it  is  about  133,000: 
then  the  lower  plants  (''cryptogams")  were  thought  to 
number  from  25,000  to  40,000,  while  now  there  are 
more  than  100,000  enumerated. 


^\^^< 


^> 


iv  PREFACE 

Another  indication  of  the  change  that  has  taken  place 
in  the  science  is  suggested  by  the  fact  that  then  the 
Plant  Kingdom  was  divided  into  the  ''Phaenogams" 
and  ''Cryptogams,"  and  that  the  usual  sequence  of  the 
study  was  first  proper  "Botany"  as  a  course  in  the 
structure,  reproduction  and  classification  of  the  "  Phaeno- 
gams,"  with  a  possible  Anhang  of  "  Cryptogamic  Botany" 
for  such  students  as  wished  to  invade  this  mysterious 
realm.  How  completely  this  has  given  way  to  a  more 
scientific  conception  of  the  Plant  Kingdom  is  shown  by 
the  practical  disappearance  of  these  terms  from  botanical 
literature  and  their  relegation  to  more  or  less  popular 
usage. 

Again,  it  was  formerly  the  very  general  practice  of 
teachers  to  present  the  subject  of  plant  study  beginning 
with  the  higher  plants,  and  indeed  devoting  the  far 
greater  time  to  them,  so  that  the  sequence  was  from  the 
higher  to  the  lower  forms.  However,  with  the  more 
complete  acceptance  of  the  doctrine  of  evolution  the 
opposite  sequence  from  the  lower  forms  to  the  higher 
has  become  the  general  rule,  since  it  permits  greater 
emphasis  to  be  placed  upon  the  progressive  structural 
changes  by  which  higher  organisms  have  been  evolved 
from  lower. 

In  the  earlier  period  there  was  not  yet  a  general  agree- 
ment as  to  the  nature  of  the  fungi,  and  their  relationship 
to  the  algae.  They  were  treated  for  the  most  part  as  a 
group  of  quite  isolated  plants  with  only  obscure  if  any 
relationship  with  other  groups.  They  were  contrasted 
Avith  other  groups,  little  attempt  being  made  to  empha- 
size similarities  in  structure,  or  to  suggest  possible  genetic 
relationships.  Today,  on  the  contrary,  we  constantly 
suggest  to  the  students  the  probabilities  as  to  the  origin 
of  each  group  of  fungi. 


PREFACE  V 

In  like  manner  the  older  botanists  of  today  remember 
the  incoming  of  the  belief  in  the  heteroecism  of  rusts, 
and  how  timorously  the  fact  was  accepted  by  teachers 
of  good  standing  among  botanists.  And  this  hesitancy 
as  to  the  acceptance  of  a  new  view  was  still  more  marked 
in  regard  to  the  nature  of  '^  lichens,"  which  by  tradition 
formerly  constituted  a  third  group  in  the  triumvirate  of 
the  lower  plants.  Algae,  Fungi  and  Lichens — the  ''thal- 
logens"  of  that  day.  Happily  we  have  outlived  this 
provincial  timidity  in  regard  to  the  starthng  conclusions 
of  the  German  botanists,  and  in  recent  years  have  calmly 
accepted  the  substitution  of  a  radically  different  system 
of  the  flowering  plants  for  that  which  had  generally  pre- 
vailed for  seventy-five  j^ears  or  more.  Many  of  us  still 
remember  that  the  Gymnosperms  used  to  be  regarded 
as  a  division  of  the  Dicotyledons,  being  sandwiched  be- 
tween the  Monocotyledons  and  the  Angiospermous 
Dicotyledons.  Now  the  Gymnosperms  are  regarded  as 
belonging  to  a  genetic  line  different  from  the  Angio- 
sperms,  although  still  associated  with  them  as  "seed 
plants." 

It  will  be  noticed  that  this  book  follows  the  usual 
German  sequence  of  Morphology  first,  followed  later  by 
Physiology.  The  experience  of  the  authors  leads  them 
to  think  that  it  is  better  to  give  the  student  a  good 
foundation  in  plant  structure  and  then  to  have  him  study 
the  plant  in  action.  However,  this  does  not  require  the 
teacher  to  defer  all  physiological  topics  until  the  com- 
pletion of  Chapters  I,  II  and  III;  indeed  it  has  been  our 
practice  to  introduce  such  topics  as  soon  as  the  student  is 
prepared  to  master  them. 

In  the  systematic  chapters  (VII  to  XX)  and  especially 
in  Chapter  XXII  the  Plant  Kingdom  is  divided  into  four- 
teen groups  of  primary  ranlv,  here  called  ''phyla."     To 


vi  PREFACE 

some  teachers  this  may  seem  to  be  an  unnecessarily 
large  number  of  primary  groups,  especially  to  those  who 
have  been  in  the  habit  of  dividing  plants  into  Thallo- 
phytes,  Bryophytes,  Pteridophytes  and  Spermatophytes, 
but  we  may  remind  all  such  that  Engler  in  the  seventh 
edition  of  his  ''Syllabus  der  Pflanzenfamilien"  divides 
the  thallophytic  plants  into  eight  primary  groups,  instead 
of  seven,  as  is  done  in  this  book.  On  the  other  hand  the 
Bryophytes,  Pteridophytes,  Calamites,  and  Lycopods 
are  brought  into  one  primary  division  by  Engler,  and  the 
Cycads,  Conifers  and  Flowering  Plants  into  another. 
We  are  assured  that  the  phyla  here  recognized  are  natural 
groups,  and  while  they  are  by  no  means  equally  separated 
from  one  another,  they  are  easily  distinguishable.  This 
is  no  less  true  for  the  phyla  below  the  Bryophytes  than 
it  is  for  those  including  and  above  this  group.  We 
feel  that  the  Calamites  and  Lycopods  are  entitled  to 
first  rank  independently  of  the  Pteridophytes,  and  that 
the  latter  and  the  Bryophytes  are  very  certainly  to  be 
treated  as  genetically  separate  phyla.  In  hke  manner 
it  seems  to  us  that  genetically  the  Cycads  and  Conifers 
are  so  remote  from  the  Flowering  Plants  that  they  can 
no  longer  be  placed  in  the  same  phylum,  and  that  they 
differ  so  much  from  one  another  that  they  must  be 
separated. 

Thirty-five  years  ago  the  treatment  here  given  the 
"  hchens"  would  have  called  for  explanation  and  defense; 
now  we  are  so  familiar  with  their  structure  that  the  sug- 
gestion that  they  were  the  first  of  the  higher  fungi  will 
cause  little  surprise.  So,  too,  there  is  less  need  now  than 
formerly  to  defend  the  treatment  of  the  Rust  Fungi, 
as  to  whose  general  relationship  there  is  less  and  less  dis- 
agreement. With  the  growing  acceptance  of  the  struc- 
tural  homology   of   ascus   and  basidium   in   the   higher 


PREFACE  vii 

fungi,  it  now  signifies  less  than  formerly  whether  the 
Rusts  are  regarded  as  related  to  the  Ascus  Fungi  or  the 
Basidium  Fungi.  As  will  be  seen  in  Chapter  XIII  we 
still  hold  to  the  theory  that  their  relationship  is  some- 
what closer  to  the  former  than  the  latter. 

For  many  years  it  has  been  evident  to  us  that  the 
apocarpous  Flowering  Plants  must  be  regarded  as  primi- 
tive and  that  from  these  the  syncarpous  forms  arose. 
Moreover  the  apopetalous  preceded  the  apetalous 
flowers,  the  latter  being  derived  from  the  former  by  a 
simplification  of  the  flower  structure.  The  flowers  of 
willows,  oaks,  elms,  nettles,  etc.,  are  quite  simple,  but 
they  are  not  primitively  so:  they  have  been  simplified 
from  more  complex  structures,  and  are  to  be  associated 
with  the  latter,  rather  than  given  place  near  the  beginning 
of  the  phylum. 

The  diagrammatic  illustrations  used  in  this  book  are 
similar  to  those  used  on  our  lecture  room  blackboards. 
We  have  felt  that  in  a  textbook  involving  laboratory  work 
elaborate  drawings  were  unnecessary  and  often  subject 
to  grave  abuse. 

It  is  scarcely  necessary  to-day  to  insist  that  this  book 
requires  a  botanical  laboratory;  nor  is  it  necessary  to 
give  ''forms"  to  be  followed  by  the  student  in  his  labora- 
tory work;  for  it  may  be  assumed  that  no  one  will  attempt 
to  use  this  book  who  has  not  himself  received  training  in 
a  good  laboratory.  We  have  purposely  suggested  many 
more  laboratory  exercises  than  can  be  performed  by  the 
ordinary  student,  affording  the  teacher  a  large  Hst  from 
which  he  may  make  his  own  selection.  A  few  suggestions 
here  as  to  this  laboratory  work  may  not  be  out  of  place, 
as  follows:  (1)  Have  each  pupil  prepare  his  own  speci- 
mens, as  far  as  possible;  only  in  a  few  special  cases  should 
he  make  use  of  specimens  prepared  by  some  one  else. 


viii  PREFACE 

(2)  Require  simple,  accurate  drawings  of  the  essential 

features  of  each  specimen.     (3)  Label  the  different  parts 

of  the  drawings,  upon  the  sheet.     (4)  Do  not  require  long 

descriptions  of  the  specimens  studied,  for  the  student 

needs  more  to  see  and  study  plants  than  to  attempt  to 

^vrite  about  them.     (5)  Do  not  ask  for  ''conclusions," 

for  the  student  has  not  yet  enough  knowledge  of  plants 

to  make  generalizations.     (G)   The  exact  name  of  the 

plant,  or  part  of  plant  studied  should  be  written  upon 

the  sheet  of  drawings. 

It  remains  only  for  us  to  say  that  while  the  junior 

author  originally  prepared  Chapters  I  to  V,  and  the  senior 

author  the  remainder,  all  have  been  gone  over  again  and 

again  by  both  of  us  so  that  we  are  both  responsible  for 

what  is  here  set  forth.     We  hope  that  this  presentation 

that   has   approved  itself  to  us  in  our   classrooms  and 

laboratories    may  be  equally  helpful  in  those  of  other 

teachers    of    Botany    in   the    Colleges    and  other  high 

schools  of  the  country. 

The   Authors. 
May,  1914 


CONTENTS 

CHAPTER  I 

Protoplasm  and  Plant  Cells  (Cytology) 

Page 
Protoplasm.     The  Plant  Cell.     Coenocytes.     Plastids.     Cell 
Inclusions.     Cell    Sap.     Formation      of      New      Cells. 
Mitosis  (Karyokinesis) 1 

CHAPTER  II 

The  Tissues  of  Plants  (Histology) 

Aggregations  of  Cells.  Differentiation  of  Cells.  Meristem. 
Parenchyma.  Sclerenchyma.  Collenchyma.  Fibrous 
Tissue.  Conductive  Tissues.  Tracheary  Tissue.  Sieve 
Tissue.     Laticiferous  Tissue      27 

CHAPTER  III 

Groups  of  Tissues,  or  Tissue  Systems  (Histology) 

In  Lower  Plants.  In  Higher  Plants.  Apical  Cells,  Der- 
matogen.  Periblem.  Plerome.  Three  Tissue  Systems. 
Epidermal  System;  Epidermis;  Hairs;  Stomata.  Con- 
ducting System;  Vascular  Bundles;  Radial  Bundles; 
Concentric  Bundles;  Collateral  Bundles;  Closed  Bundles; 
Open  Bundles.  Secondary  Thickening.  Supporting 
System;  Collenchyma  Strands;  Fibrous  Strands.  Pali- 
sade Parenchyma.  "Sponge"  Parenchyma.  Storage 
Parenchyma.     Cork.     Lenticels 43 

CHAPTER  IV 

Plant  Physiology 

Nutrition;  Water;  Imbibition;  Osmosis;  Turgor;  Path  of  the 
Water;  Evaporation  of  Water;  Root  Pressure;  Solutions; 
ix 


X  CONTENTS 

Page 
Mineral  Nutrients;  Photosynthesis;  Carbohydrates;  Pro- 
teins; Root  Nodules;  Hysterophytic  Plants;  Respiration; 
Anaerobic  and  Aerobic  Respiration;  Fermentation;  Tem- 
perature Relations;  Effect  of  Poisons.  Growth;  Relation 
to  Nutrition, Temperature,Light.  Reproduction;  Asexual, 
and  Sexual;  Behavior  of  Chromosomes,  Diploid  and  Hai> 
loid  Number;  Inheritance;  Mendelism;  Natural  Selec- 
tion; Survival  of  the  Fittest;  Variations;  Mutations; 
Evolution;  Phylogeny;  Plant  Breeding.  Movements; 
Hygroscopic  Movements;  Protoplasmic  Movements; 
Turgor  Movements;  Growth  Movements,  Nutation, 
Tropisms,  Phototropism,  Geotropism,  Thigmotropism, 
Chemotropism,  Hydrotropism.  Pathology;  "Physiolog- 
ical Diseases;"  Diseases  due  to  Parasites 71 

CHAPTER  V 

The  Chemistry  of  the  Plant 

Inorganic  Acids  and  Salts.  Organic  Acids.  Alcohols.  Fats 
and  Fatty  Oils.  Aromatic  Oils  and  Camphors.  Carbo- 
hydrates; Monosaccharids;  Disaccharids;  Trisaccharids ; 
Tetrasaccharids;  Polysaccharids.  Glucosides.  Alkaloids. 
Protein  Group.     Enzymes.     Miscellaneous  Substances  .    139 

CHAPTER  VI 

The  Classification  of  Plants 

Number  of  Species.  Relationship.  Species  and  Genera. 
Higher  Groups;  Families;  Orders;  Classes;  Phyla.  Evo- 
lution. Origin  of  Phyla.  The  Place  of  Plants  in  Time. 
Table  of  Geologic  Time  Divisions l.")7 


CHAPTER  VII 

Phylum  I.     Myxophyceae:  Slime  Algae 

General  Characters.    Two  Classes.    Blue  Greens;  Unicellular; 

Filamentous.     Bacteria.     Higher  Blue  Greens      ....    163 


CONTENTS  xi 

CHAPTER  VIll 
Phylum  II.     CHLOROPHYfEAE:  Simple  Algae 

Page 
CJeneral  Characters.     Two  Classes.     Green  Slimes;   Palinel- 
lales;   Coenohiales.     Confervas;   Ulothrix;   Oedop;oniiun; 
Disk  Algae 170 

CILVPTER  IX 

Phylum  III.     Zygophyceae:  Conjugate  Algae 

General  Characters.     Two  Classes.     Pond  Scums;  Desmids. 

Diatoms.     Origin  of  ZygophA^ceae 177 

CHAPTER  X 

Phylum  IV.     Siphonophyceae:  Tube  Algae 

General  Characters.  Lower  Tube  Algae;  Water  Flannel; 
Green  Felts.  Tube  Fungi;  Water  Molds;  Downy  Mil- 
dews; Black  Molds;  Insect  Fungi.  Higher  Tube  Algae; 
Bladder  Algae;  Sea  Ferns;  Sea  Umbrellas;  Stoneworts. 
Summary 184 

CHAPTER  XI 

Phylum  V.     Phaeophyceae:  Brown  Algae 

General  Characters.  Origin.  Ectocarpus.  Kelps.  Rock- 
weeds.     Gulfweeds 199 

CHAPTER  XII 

Phylum  VI.     Rhodophyceae:  Red  Algae 

General  Characters.  Cell-walls.  Color.  Reproduction. 
"Laver."  Nemalion.  Corallina.  Polysiphonia.  "Irish 
Moss" 205 


xii  CONTENTS 

CHAPTER  XIII 
Phylum  VII.     Carpomyceteae:  Higher  Fungi 

Page 
General  Characters.  Reproduction.  Three  Classes.  Asciis 
Fungi;  Disk  Lichens;  Cup  Fungi;  Morels;  Slit-Fungi; 
Closed  Fungi;  Mildews;  Yeast-plants;  Truffles.  Basid- 
ium  Fungi;  False  Tubers;  Puff-balls;  Bird-nest  Fungi; 
Stink-horns;  Toadstools.  Brand  Fungi;  Rusts,  Heter- 
oecism,  Wheat  Rust,  Sexual  Reproduction;  Smuts,  Corn 
Smut,  Wheat  Smut,  Bunt.  Imperfect  Fungi;  Spot- 
Fungi;  Black-dot  Fungi;  Molds 211 

CHAPTER  XIV 

Phylum  VIII.     Bryophyta:  Mossworts 

General  Characters.  Life  Cycle.  Two  Classes.  Liverworts; 
Riccia;  Hornworts;  Great  Liverwort;  Scale-Mosses. 
Mosses;  Reproduction;  Protonema;  Black  Mosses;  Peat 
Mosses;  True  Mosses 242 

CHAPTER  XV 

Phylum  IX.     Pteridophyta:  Ferns 

General  Characters.  Life  Cycle.  Two  classes.  Old-fash- 
ioned Ferns;  Adder  Tongues;  Marattias;  Quillworts. 
Modern  Ferns;  Land  Ferns;  Water  Ferns 254 

CHAPTER  XVI 

Phylum  X.     Calamophyta:  Cal.\mites 

General  Characters.      Wedge-leaved    Calamites.      Horsetails. 
Old  Calamites 261 

CHAPTER  XVII 
Phylum  XI.     Lepidophyta:  Lycopods 

General  Characters.    Two  Classes.    Lower  Lycopods;  Ground 

Pines.     Club  Mosses;  Selaginellas;  Lepidodendrids  .    .    .   266 


CONTENTS  xiii 

CHAPTER  XVIII 

Phylum  XII.     Cycadophyta:  Cycads 

Page 
General     Characters.       '\Seed-ferns."      Common     Cycads. 
"  Flowering    Plant    Ancestors."           Conifer    Ancestors. 
Maidenhair  Trees.     Joint-firs 271 

CHAPTER  XIX 

Phylum  XIII.     Strobilophyta:  Conifers 

General  Characters.    Taxodiums.    Old  Pines.    Modern  Pines, 

Genera  of  Modern  Pines.     Cypresses.     Junipers.     Yews.  277 

CHAPTER  XX 

Phylum  XIV.     Anthophyta:  Flowering  Plants 

General  Characters.  Typical  Flower;  Buttercup;  Water 
Plantain;  Strawberry.  Two  Classes.  Monocotyledons; 
Lilies;  Calla  Lilies;  Palms;  Grasses;  Amaryllises;  Orchids. 
Dicotyledons;  Axis  Flowers,  Magnolia,  Mallow,  Gera- 
nium, Violet,  Mustard,  Pink,  Primrose,  Phlox,  Petunia, 
Snapdragon,  Sage;  Cup  Flowers,  Spiraea,  Rose,  Apple, 
Plum,  Pea,  Currant,  Evening  Primrose,  Prickly  Pear, 
Walnut,  Oak,  Parsnip,  Honeysuckle,  Sunflower,  Dande- 
lion. Summary  of  Anthophyta;  Evolution;  Progressive 
Development  through  the  Phyla 284 

CHAPTER  XXI 

Some  Special  Adaptations 

Plant  Body;  Thorns;  Storage  Organs;  Mesophytes;  Xero- 
phytes;  Hydrophytes;  Parasites.  The  Flower;  Anemo- 
pliilous;  Entomophilous;  Colors  and  Odors;  Nectar; 
Actinomorphic;  Zygomorphic;  Proterogynous ;  Protcran- 
drous;. Dimorphic;  Parthenogenesis.     Seed  Distribution.  319 


XIV  CONTENTS 

CHAPTER  XXH 
The  Plant  Phyla 

Page 
Number  of  Classes,  Orders,  Families,  and  Species.     Key  to  the 
Phyla.     Systematic  Arrangement  of  the  Fourteen  Plant 
Phyla 327 

Ini>ex 381 


N.  Q.  COLLEGE  OF  A,  &  M.  A. 


ESSENTIALS  OF  COLLEGE 
BOTANY 

CHAPTER  I 

PROTOPLASM  AND  PLANT  CELLS 
CYTOLOGY 

1.  Protoplasm.  Plants,  like  animals,  possess  as  their 
living  portion  a  soft,  viscid,  more  or  less  granular  sub- 
stance called  protoplasm.  This  living  matter  makes  up, 
ordinarily,  only  a  rather  small  proportion  of  the  total 
substance  of  the  larger  plants,  being  present  in  larger 
proportion  in  the  smaller,  simpler  organisms.  In  the 
rapidly  growing  parts  of  plants  it  is  far  more  abundant 
than  in  the  fully  developed  organs. 

2.  Protoplasm,  when  studied  under  high  magnifica- 
tions with  the  use  of  certain  stains,  is  found  not  to  be  a 
homogeneous  substance  but  to  occur  in  various  forms 
as  follows:  (1)  Cytoplasm.  This  is  the  bulk  of  the  pro- 
toplasm and  that  which  probably  performs  most  of  its 
ordinary  functions.  It  is  less  dense  than  the  other  forms, 
being  often  of  about  the  consistency  of  the  white  of  an 
egg.  It  appears  to  consist  of  a  clear,  more  or  less  liquid 
portion  in  which  are  imbedded  innumerable  granules  of 
all  sizes,  from  those  easily  visible  under  moderately  high 
magnification  to  those  barely  visible  at  the  highest  possi- 
ble magnification.  (2)  Nucleus.  This  is  a  somewhat 
denser  portion  of  the  protoplasm,   usually  of  definite 

1 

ntOPERTY  LIBRARY 

N.  C.  State  College 


2  PROTOPLAS:\I  AND  PLANT  CELLS 

shape  (mostly  rounded)  and  separated  from  the  cyto- 
pkism  by  a  delicate  membrane.  Like  the  cytoplasm,  the 
bulk  of  the  nucleus  seems  to  be  a  colorless  fluid  in  which 
is  found  a  network  of  fine  threads  (the  linin  network) 
on  which  occur  more  or  less  numerous  coarser  or  finer 
granules  of  chromatin.  A  rounded,  usually  nearly  homo- 
geneous body,  the  nucleolus,  is  mostly  visible  as  a  small, 
highly  refractive  drop  within  the  nucleus.  (3)  Centro- 
some.  Although  of  general  occurrence 
throughout  the  animal  kingdom  centro- 
somes  are  definitely  known  only  in  certain 
of  the  lower  plants.  In  a  cell  not  in  divi- 
sion the  centrosome  appears  as  a  minute 
piaim  enclosed  by  body  lYi  closc  proximity  to  the  nucleus.     It 

a  cell  wall.  ,i  ,•  ■•  i  ,... 

takes  an  active  part  m  nuclear  division  in 
animals,  and  possibly  may  do  so  in  those  plants  in 
which  it  is  present.  (4)  Plastids.  These  consist  of 
denser  masses  of  protoplasm  lying  in  the  cytoplasm 
and  are  colorless  (leucoplasts)  or  colored  (chloroplasts 
and  chromoplasts).  They  are  lacking  in  the  cells  of 
many  plants. 

3.  All  these  forms  of  protoplasm  possess  many  char- 
acteristics in  common,  both  as  to  physical  and  chemical 
structure.  They  are  very  complex  compounds  with 
most  of  the  characteristics  belonging  to  the  proteins  but 
differing  from  them  in  some  important  points.  Proto- 
plasms consist  mainly  of  carbon,  hydrogen,  oxygen,  nitro- 
gen and  sulphur  and  of  phosphorus  also  in  the  case  of 
the  nucleus.  In  all  probability  certain  metallic  elements 
also  enter  into  the  combination. 

4.  The  most  remarkable  property  of  protoplasm  and 
that  which  distinguishes  it  from  all  other  chemical  sub- 
stances is  its  power  of  manufacturing  new  protoplasm 
out  of  simpler  substances,  in  other  words,  the  power  of 


PROPERTIES  OF  PROTOPLASM        3 

growth  and  reproduction.  In  addition,  protoplasm  pos- 
sesses in  great  degree  the  power  of  movement  as  well  as 
of  perception.  Motion  is  not  always  evident  but  in  cer- 
tain stages  at  least  it  can  almost  always  be  found.  The 
protoplasm  may  move  as  a  whole  or  certain  portions  of 
the  cytoplasm  may  stream  to  and  fro  in  a  most  compli- 
cated manner.  Such  streaming  may  affect  only  the  small 
granules,  or  the  larger  bodies  such  as  nucleus  and  plastids 
may  be  transported  from  one  place  to  another. 

5.  Protoplasm  possesses  the  power  of  imbibition  of 
water.  It  may  imbibe  so  much  water  that  it  becomes 
very  thin  and  watery  and  yet  still  retain  its  powers  of 
motion  and  of  reproduction.  There  is  a  limit,  however, 
to  the  amount  of  water  protoplasm  will  imbibe,  for  some 
of  the  naked  masses  of  protoplasm  set  free  by  some 
plants  for  reproductive  purposes  retain  their  shape  and 
size  in  spite  of  being  immersed  in  water. 

6.  The  complex  chemical  and  physical  structure  of 
protoplasm  renders  it  very  susceptible  to  injur}'-.  This 
injury  may  be  simply  physical,  or  certain  of  the  groups 
of  atoms  making  up  the  complex  protoplasmic  molecule 
may  be  changed  chemically  in  such  a  way  that  the  proper 
functions  can  not  be  carried  on.  When  the  changes  reach 
such  a  point  that  on  removal  of  these  external  unfavorable 
conditions  the  protoplasm  does  not  resume  its  functions, 
we  say  that  death  has  occurred.  Heat,  cold,  electricity, 
even  light,  also  mechanical  injury  such  as  crushing,  as 
well  as  innumerable  chemicals  will  cause  death.  Many 
of  these  agents  when  applied  in  smaller  amounts  or  to 
a  lesser  degree  check  the  functions  of  protoplasm  only 
temporarily.  Thus  a  jar  or  sudden  cooling  will  check 
for  a  time  the  streaming  within  the  protoplasm. 

7.  All  of  the  modifications  of  protoplasm  are,  at  least 
when  active,   in  a  more  or   less  liquid  state.     The  two 


4  PROTOPLASM  AND  PLANT  CELLS 

theories  as  to  its  physical  structure  that  receive  the 
strongest  support  are  the  emulsion  and  the  fibrillar 
theories  respectively.  By  the  first  theory  protoplasm 
is  a  very  complex  emulsion  of  various  substances  more 
or  less  closely  related  chemically.  The  bodies  appear- 
ing as  granules  would  be  then,  in  part  at  least,  small 
drops  suspended  in  the  emulsion.  These  drops  are 
perhaps  themselves  also  emulsions.  The  fine  lines  visi- 
ble under  certain  conditions  would  be  not  fine  strands 
but  rather  the  edges  of  surfaces  separating  adjacent 
units  of  the  emulsion.  It  is  readily  seen  that  this  theory 
would  accord  well  with  the  observed  fact  of  the  great 
power  of  imbibition  of  water  by  the  protoplasm,  for  this 
would  but  separate  the  droplets  of  the  emulsion  some- 
what more  without  necessarily  disturbing  their  relative 
positions.  The  viscidity  or  relative  firmness  of  some  pro- 
toplasm (e.g.  plastids  and  nucleus)  is  in  agreement  with 
what  we  know  about  emulsions.  Thus  two  thin  liquids 
may  sometimes  be  brought  to  such  a  state  of  emulsion 
that  the  whole  mass  is  firm  and  will  stand  upright.  The 
fibrillar  theory  supposes  that  the  delicate  lines  mentioned 
above  are  fine  threads,  connected  at  innumerable  points 
and  traversing  the  clear  liquid  making  up  the  bulk  of  the 
protoplasm.  The  granules  are  looked  upon  as  being 
situated  on  these  fibrillac  or  sometimes  in  the  spaces 
between  them. 

8.  The  Plant  Cell.  In  all  plants  we  find  that  the 
protoplasm  occurs  in  definite  units  which  are  independ- 
ent or  more  or  less  connected  with  neighboring  units;  in 
the  latter  case  the  whole  mass  of  these  units  constitutes 
the  plant.  These  units  are  called  cells  and  consist 
always  of  at  least  two  parts,  a  mass  of  cytoplasm  and  a 
nucleus.  In  most  plant  cells  the  protoplasm  deposits  a 
firmer  substance  as  a  box-like  covering  called  the  cell  wall, 


CELL  WALL  5 

which  gives  firmness  to  the  cell  and  acts  as  a  protection 
to  it.  Plastids  are  very  frequent  constituents  of  cells 
although  large  groups  of  the  lower  plants,  the  so-called 
fungi,  lack  them  entirely.  Most  cells  contain  spaces 
within  the  cytoplasm  filled  with  watery  solutions.  These 
are  called  vacuoles,  and  the  contained  solutions  are 
known  as  cell  sap.  At  its  outer  surface  as  well  as  at  the 
surfaces  in  contact  with  the  larger  vacuoles  and  the 
nucleus  the  cytoplasm  forms  a  denser  layer,  free  from 
granules,  which  holds  the  cytoplasm  in  shape,  prevents 
passage  of  certain  substances  into  or  out  of  the  cyto- 
plasm, etc.  This  is  the  plasma  membrane.  The  plasma 
membrane  about  the  nucleus  is  usually,  however,  called 
the  nuclear  membrane.  The  layer  next  to  the  vacuoles 
is  frequently  spoken  of  as  the  tonoplast. 

9.  The  cell  wall  consists  usually  of  cellulose  or  related 
substances,  i.e.  of  some  of  the  more  complex  carbohy- 
drates. These  are  composed  of  carbon,  hydrogen  and 
oxygen  in  the  proportion,  usually,  of  six  parts  of  carbon, 
ten  of  hydrogen  and  five  of  oxygen.  In  many  of  the 
fungi  and  some  other  plants  the  cell  wall  is  composed  of 
a  form  of  chitin,  containing  nitrogen  in  addition  to  the 
substances  mentioned.  This  has  been  called  fungus 
cellulose,  although  not  related  to  cellulose  chemically. 
In  the  walls  of  older  cells  there  are  frequently  deposited 
various  other  substances  such  as  silica  in  the  diatoms 
and  in  the  epidermal  cells  of  joint  rushes  and  grasses, 
suberin  and  cutin  in  the  walls  of  cork  and  epidermal  cells, 
respectively,  hadromal,  or  perhaps  vanillin  and  conif- 
erin  in  wood  cells,  etc.,  these  being  in  part  the  so-called 
''Ugnin"  of  earlier  botanical  works.  Aside  from  cellu- 
lose the  chief  constituent  of  cell  walls  is  pectose,  chemi- 
cally very  similar  to  it  and  frequently  mixed  with  it. 
Under    the    influence    of    certain    not    well    understood 


6  PROTOPLASM  AND  PLANT  CELLS 

conditions  the  cellulose  or  pectose  may  become  changed 
into  gums,  e.g.  gum  arable,  cherry  gum,  slime  of  flax- 
seed, etc. 

10.  The  cell  wall  when  first  formed  is  very  thin. 
Growth  occurs  either  by  apposition  (deposition  of  cell 
wall  substance  on  the  inner  surface  of  the  wall)  in  which 
case  the  wall  becomes  thicker  and  may  or  may  not 
appear  layered,  or  by  intussusception  (the  deposition  of 
new  material  among  the  particles  of  the  old),  in  which 
case  the  wall  becomes  larger  as  well  as  often  thicker. 
The  first  laj^er  formed  is  the  thin  middle  lamella.  Upon 
this  is  deposited,  on  either  side,  a  thicker  layer  of  some- 
what different  composition,  the  secondary  lamella.  A 
tertiary  lamella  is  sometimes  formed  also.  These 
different  layers  are  usually  of  somewhat  different  chemi- 
cal composition.  Thus  the  middle  lamella  is  often  com- 
posed of  calcium  pectate  or  some  other  pectose  compound 
while  the  secondary  lamellae  are  cellulose  or  a  mixture 
of  cellulose  with  other  substances.  When  present,  the 
tertiary  lamella  is  usually  nearly  pure  cellulose. 

11.  The  walls  between  adjacent  living  cells  are  quite 
generally  perforated  by  very  minute  pores  through  which 
delicate  fibrils  of  cytoplasm  extend  from  one  cell  to  the 

other,  apparently  thus  binding  all  the 
living  cells  of  the  plant  together  into  one 
more  or  less  coordinated  unit. 

12.  The  thickening  of  the  cell  wall  is 
not  always  uniform.  Indeed,  except  in 
Fig.  2.— Thick-  Comparatively  thin-walled  cells  thinner 
areas  or  spots  are  almost  always  left  be 
tween  the  more  thickened  parts.  These  thickenings  may 
be  ridges  which  are  in  the  shape  of  rings,  spirals  or  reticu- 
lations or  may  occupy  so  much  of  the  surface  that  the 
unthickened  parts  appear  as  pits.     Usually  these  thick- 


CHARACTERISTICS  OF  CELLS  7 

enings  are  on  the  inner  surface  of  the  cell  wall,  but  in 
many  spores  (e.g.  pollen  grains  or  spores  of  ferns  or  fungi) 
they  are  external.  This  is  also  the  case  in  some  of 
the  lower,  one-celled  plants  such  as  desmids.  The 
thickenings  have  various  functions,  such  as  strengthen- 
ing the  wall,  providing  means  for  transportation  (in  the 
case  of  spores  and  pollen  grains  which  sometimes  depend 
upon  animals  for  their  dispersal,  the  rough  projections 
enabling  them  to  cling  to  the  animal),  etc. 

13.  After  attaining  their  full  differentiation  most  of 
the  cells  of  the  higher  plants  (at  least  of  the  woody 
plants)  die,  their  cell  walls  remaining  to  make  up  the 
bulk  of  the  plant  body.  We  usually  continue  to  speak 
of  such  dead,  empty  cell  walls  as  cells,  although  the 
essential  parts,  the  cytoplasm  and  nucleus,  may  have 
disappeared  long  ago. 

14.  Cells  vary  greatly  in  size,  those  of  some  of  the 
bacteria  being  less  than  half  a  micron  (i.e.  less  than  one- 
fifty-thousandth  of  an  inch)  in  diameter,  wdiile  the  egg 
cell  of  Zamia  may  have  a  thickness  of  over  a  millimeter 
and  a  length  of  3  mm.  (i.e.  a  volume  over  twenty  billion 
times  as  great),  the  egg  cell  of  Dioon  being  even  larger. 
Some  fiber  cells  have  a  length  of  many  centimeters,  e.g. 
bast  fibers  of  ramie  {Boehmeria  nivea). 

15.  In  some  of  the  lower  aquatic  plants  occur  repro- 
ductive cells  with  no  cell  walls  (e.g.  zoospores,  tetra- 
spores,  etc.).  These  cells  are  frequently  motile  by  means 
of  protoplasmic  processes  called  cilia  or  flagella.  Such 
cells  in  many  cases  settle  down  and,  becoming  attached 
to  something,  form  a  cell  wall  before  proceeding  further 
in  their  development.  Even  in  the  higher  plants  the  egg 
and  sperm  cells  are  naked. 

16.  Typical  cells  have  but  a  single  nucleus.  In  certain 
stages  of  the  life  history  of  some  groups  of  plants  the 


8  protoplas:m  and  plant  cells 

cells  are  binucleate  while  they  are  uninucleate  in  the 
remaining  stages.  In  some  groups  of  plants,  however, 
we  find  that,  enclosed  in  an  outer  cell  wall,  there  is  a 
mass  of  cytoplasm  containing  many  nuclei.  Such  a 
structure  is  called  a  coenocyte.  It  is  frequently  re- 
garded as  consisting  of  as  many  cells  as  nuclei  are  present, 
not  separated,  however,  by  partition  w^alls.  Perhaps  it 
may  better  be  considered  as  a  sort  of  compound  cell  as 
the  nuclei  do  not  seem  to  control  definite  masses  of  cy- 
toplasm. In  some  coenocytes  of  the  seaweed  Griffithsia 
over  4,000  nuclei  are  present,  while  in  the  enormous 
coenocyte  of  Caulerpa,  likewise  a  seaweed,  which  often 
attains  a  length  of  several  decimeters,  the  number  of 
nuclei  is  vastly  greater.  Coenocytes  are  mostly  re- 
stricted to  certain  groups  of  lower  plants,  but  cells  of 
coenocytic  nature  may  occur  even  in  the  higher  plants. 

17.  In  shape  cells  are  very  variable.  Usually  we  find 
that  free-living  cells  approach  the  spherical  shape  al- 
though they  are  often  elongated  somewhat.  Cells 
united  to  other  cells  are  usually  flattened  on  the  sides 
where  they  are  in  contact.  When  surrounded  by  cells 
at  all  sides  cells  are  usually  more  or  less  regular,  several 
to  many-sided  polyhedra.  Some  cells  are  cylindrical 
while  often  we  have  fiber  or  spindle  shaped  cells.  Some 
cells  are  lobed  or  branched. 

Laboratory  Studies.  It  is  assumed  that  the  attempt  will 
not  be  made  to  use  this  book  without  endeavoring  to  carry 
out  in  the  laboratory  all  or  at  least  a  selection  of  the  laboratory 
exercises  suggested  here  and  there  in  connection  with  the 
various  topics.  So  far  as  possible  the  suggested  exercises 
have  been  made  simple  enough  for  the  student  to  undertake 
himself,  depending  as  little  as  possible  upon  specimens  prepared 
or  experiments  set  up  by  the  teacher.  It  is  absolutely  essential 
that  each  student  have  the  use  of  a  good  compound  micro- 
scope, and  that  he  possess  the  proper  tools  for  making  sections, 


LABORjVTORY  STUDIES  9 

etc.,  as  well  as  a  few  siini)le  reagents  such  as  alcohol,  iodinc- 
potassium-iodide  solution,  potash  solution,  etc.  The  measure- 
ments used  throughout  this  book  arc  metric;  1  cm.  =  0.394  in. 
1  mm.  =  about  1/25  inch,  1  micron  (written  At)=  0.001  mm. 
(i.e.  about  one-twcnt3''-five-thousandth  of  an  inch). 

(a)  ]\Iake  a  thin  longitudinal  section  of  the  tip  of  a  large 
root  of  Indian  corn  or  hyacinth  or  any  other  plant  with  stout 
roots,  or  of  the  growing  point  of  a  herbaceous  stem,  and 
mount  in  water  and  examine  under  the  microscope.  The 
small  cells  near  the  tip  will  be  found  to  be  full  of  protoplasm. 
The  following  tests  should  be  made  on  different  sections:  (1) 
Add  strong  iodine  solution;  this  turns  the  protoplasm  brown 
or  yellowish  brown.  (2)  Test  with  a  drop  or  two  of  Millon's 
reagent  (dissolve  a  small  amount  of  mercury  in  an  equal  weight 
of  strong  nitric  acid,  and  dilute  with  an  equal  amount  of 
distilled  water.  Use  fresh):  the  protoplasm  is  turned  bright 
yellow.  (3)  Mount  a  section  in  strong  sugar  solution  and 
after  a  few  moments  add  a  drop  of  fairly  strong  sulphuric 
acid:  the  protoplasm  is  stained  red  or  pink.  (4)  Treat  a 
section  with  nitric  acid  and  then  with  strong  potash:  the  yellow 
color  of  the  protoplasm  shows  the  so-called  xanthoprotein 
reaction. 

(6)  Repeat  these  tests  with  raw  white  of  egg,  which  consists 
of  proteins.  Note  that  the  results  are  the  same.  For  the 
sulphuric-acid-sugar  test  it  is  more  satisfactory  to  mix  the  egg 
white  with  a  strong  sugar  solution  in  a  test  tube,  rolhng  the 
latter  so  that  the  sides  are  moistened  with  the  mixture.  Now 
very  carefully  run  a  small  drop  of  concentrated  sul])huric  acid 
down  the  side  of  the  tube.  This  browns  the  solution  where 
it  comes  in  contact  in  most  concentrated  form  but  at  the  edge 
of  its  path  and  at  its  point  of  entrance  into  the  mixture  tlie 
red  coloration  is  shown  beautifull}^ 

(c)  To  study  the  motion  of  cytoplasm  make  a  cross  or 
longitudinal  section  of  a  stem  (the  upper,  younger  portion)  of 
Petunia  or  tomato  without  injuring  the  hairs.  JMount  in 
water  and  examine  a  cell  of  a  hair.  The  cytoplasm  will 
usually  be  found  to  be  streaming.  Note  that  the  streams  seem 
frequently  to  center  upon  the  nucleus.  Note  the  effect  upon 
the  motion  of  placing  the  slide  on  a  jiiece  of  ice.  Warm  it  up 
again  to  a  temperature  of  about  30°  to  35°  C.  and  note  the 


10  PROTOPLASM  AND  PLANT  CELLS 

results.  Heat  to  55°  to  60°  C.  Now  cool  to  about  30°. 
Examine  again. 

{(I)  On  similar  specimens  test  the  effect  upon  motion  of 
iodine  solution,  alcohol,  glycerine,  etc. 

(e)  Various  types  of  proto])lasmic  motion  may  be  found  in 
the  long  cells  of  the  young  silk  of  Indian  corn,  in  the  cells  of 
the  leaves  of  water  weed  (Philotria),  the  cells,  especially  those 
near  the  ends  of  the  shoots,  of  Chara  or  Nitella,  etc. 

(/)  To  observe  the  different  parts  of  a  cell  study  again  the 
stem  hairs  of  Petunia.  Note  nucleus,  nucleolus  cytoplasm, 
vacuoles,  cell  wall.  Cells  from  the  leaf  of  a  moss  may  also  be 
used  for  this  purpose. 

(g)  Bring  into  the  laboratory  some  growing  LTlothrix, 
Cladophora,  Stigeoclonium  or  other  zoospore-producing  algae, 
and  place  in  fresh  water  near  the  window.  In  a  few  hours  one 
can  often  find  myriads  of  zoospores.  Examine  these  for  cells 
lacking  walls  and  provided  with  motile  organs  (flagella). 

(h)  Make  a  thin  cross-section  of  a  herbaceous  stem.  Treat 
with  iodine  solution  and  then  with  somewhat  diluted  sulphuric 
acid.  Cellulose  walls  are  turned  blue,  cutinized  and  lignificd 
(wood)  walls,  yellowish  brown.  Stain  another  section  with 
anilin-water  safranin.  This  stains  cutin  walls  yellowish  and 
lignin  walls  bluish. 

(i)  Examine  a  thread  of  green  felt  (Vaucheria)  or  a  vegeta- 
tive thread  of  bread  mold  (Mucor)  for  a  plant  of  coenocytic 
structure.  Note  the  lack  of  cross  walls.  The  numerous 
minute  nuclei  are  not  visible  without  staining. 

ij)  The  stone  cells  making  up  the  shells  of  various  nuts  are 
good  objects  to  show  the  deposition  of  the  cell  wall  in  layers, 
i.e.  by  apposition.  With  a  pocket  knife  cut  as  thin  a  section  as 
possible,  and  place  it  in  water  containing  a  httle  potash.  At 
the  edges  may  be  found  areas  thin  enough  for  examination. 
Here  and  there  in  the  plainly  layered  cell  wall  will  be  found 
pits,  i.e.  thin  places  left  when  the  rest  of  the  wall  thickened. 

18.  Plastids.  Three  kinds  of  plastids  occur  in  plants. 
They  all  agree  in  general  structure  in  that  they  are  denser 
bodies  of  protoplasm  imbedded  in  the  cytoplasm.  They 
may  have  many  shapes  but  are  more  frequently  round  or 
elliptical  in  outline.     So  far  as  is  certainly  known  new 


PLASTID8  11 

plastids  are  formed  only  from  the  division  of  old  plastids 
into  two  parts.  They  are  difficultly  visible  in  some  plant 
cells,  e.g.  in  the  small  rapidly  dividing  meristem  cells  at 
the  growing  points  of  a  plant,  and  are  entirely  lacking  in 
some  great  groups  of  plants,  viz.  the  bacteria  and  fungi. 
19.  Chloroplasts  are  plastids  containing  chlorophyll. 
Ordinarily  they  are  green,  from  the  color  of  the  chloro- 
phyll itself,  but  in  some  groups  of  plants  the  green  color 
is  masked  by  the  presence  of  other  pigments  in  the  chloro- 
plasts in  addition  to  the  chlorophyll.  Thus 
in  the  Red  Seaweeds  (Rhodophyceae)  the 
chloroplasts  are  usually  red,  in  the  Brown 
Algae  (Phaeophyceae)  they  are  brown,  in 
some  ]\Iyxophyceae  the  chloroplasts  are 
bluish  green,  etc.  Chlorophyll  proper  is 
a  bluish  green,  apparently  somewhat  oily  p^^  3— piistida 
substance,  probably  contained  in  inter-  (cMoropiasts)  in  a 
stices  of  the  chloroplast.  It  is  soluble 
in  alcohol,  by  means  of  which  it  can  be  removed,  leav- 
ing the  chloroplast  colorless.  In  addition  to  chlorophjdl 
most  chloroplasts  contain  an  orange  yellow  pigment,  to 
which  the  name  xanthophjdl  is  often  applied.  It  ap- 
pears to  be  a  form  of  carotin.  The  mixture  of  these 
two  gives  the  grass-green  color  to  the  chloroplast.  With 
rare  exceptions  chlorophyll  is  not  produced  in  the  ab- 
sence of  light.  It  usually  disappears  in  prolonged  dark- 
ness, leaving  the  chloroplast  stained  yellow  with  xantho- 
phyll  or  colorless.  In  many  of  the  lower  plants  the 
chloroplasts  are  of  various  shapes,  often  being  star-, 
band-,  plate-,  or  even  net-shaped.  In  the  higher  plants 
they  are  mostly  more  or  less  disk  shaped.  In  some  of 
the  liverworts  and  many  of  the  algae  they  contain  one 
or  more  highly  refractive  bodies,  called  pyrenoids,  which 
are  probably  crystals  of  some  albuminous  substance. 


12  PROTOPLAS:\r  AND  PLANT  CELLS 

20.  Leucoplasts  are  colorless  plastids  occurring  in  the 
parts  of  the  plant  not  exposed  to  light.  When  exposed 
to  light  they  usually  produce  chlorophyll  and  become 
green,  showing  that  they  are  essentially  the  same  as  the 
chloroplasts.  They  are  abundant  in  parts  of  the  plant 
where  starch  is  being  stored  up. 

21.  Chromoplasts  are  found  in  the  cells  of  many 
flowers  and  fruits  and  other  colored  parts  of  plants. 
They  are  small,  round  or  angular  or  needle  shaped 
plastids,  mostly  red  or  yellow  in  color.  They  contain 
carotin  or  other  coloring  matters  but  no  chlorophyll. 
In  many  cases  they  are  directly  developed  from  chloro- 
plasts by  the  loss  of  chlorophyll  and  the  development  of 
some  other  pigment. 

Laboratory  Studies. — (a)  Mount  a  leaf  of  moss  and  examine 
for  chloro})Iasts. 

(6)  Soak  a  few  moss  leaves  in  strong  alcohol  for  twenty-four 
hours  and  note  the  decoloration  of  the  chloroplasts. 

(c)  Examine  Sj^irogyra  for  spiral,  ribbon-shaped,  or  Zygnema 
for  star-shaped  chloroplasts. 

(^/)  Soak  a  handful  of  leaves  in  alcohol  for  several  hours.  If 
the  flask  containing  the  alcohol  and  leaves  be  placed  in  hot 
water  the  extraction  of  the  chlorophyll  will  progress  more 
rapidly.  Note  the  green  color  of  the  extract.  Add  a  little 
gasoline  or  benzine  (not  benzene,  i.e.  benzol)  to  the  alcoholic 
solution  and  shake  thoroughly  and  then  let  it  stand  until  the 
alcohol  and  gasoline  separate.  The  chlorophyll  will  be  found 
now  in  the  gasoline,  the  carotin  remaining  in  the  alcohol. 

(e)  Examine  the  cells  of  various  fungi,  e.g.  toadstools, 
puf'fballs,  molds,  etc.,  or  of  a  parasitic  flowering  plant,  e.g. 
dodder  (Cuscuta),  and  note  the  absence  of  chloroplasts. 

(/)  Sprout  a  potato  in  darkness.  Make  a  section  of  its  stem 
and  compare  with  a  similar  section  of  the  stem  of  a  potato 
grown  in  light.  Note  the  leucoplasts  in  the  former  and  the 
chloroplasts  in  the  latter.  Similarly  compare  the  stomatal 
guard  cells  of  the  epidermis  of  green  and  l)lanched  celery. 

{g)  Examine   the   cells   of  a   carrot  root  for   chromoplasts 


CELL  INCLUSIONS 


13 


stained  with  carotin.  Examine  also  the  red  cells  of  a  ripe 
tomato  or  the  yellow  cells  of  a  petal  of  nasturtium  (Tropaeo- 
lum)  or  the  cells  of  rose  hips. 

22.  Cell  Inclusions.  Within  many  cells  are  often 
found  bodies  not  living  and  not  an  essential  part  of  the 
cell  but  which  have  been  produced  by  the  cell  itself. 
They  may  be  temporary  or  permanent.  They  may  lie 
in  the  cytoplasm,  in  the  vacuoles  or  in  the  plastids. 
Such  bodies  are  called  cell  inclusions.  The  most  fre- 
quent cell  inclusions  are  starch,  aleuron,  crystals  and 
sometimes  drops  of  fat  or  oil. 

23.  Starch.  In  the  green  cells  of  many  plants  there 
are  produced  in  the  chloroplasts  on  exposure  to  light 
small   pearly   white  grains   of    starch. 

These  are  usually  transformed  into 
sugar  during  the  night  and  used  by  the 
plant  for  food  or  transported  to  some 
other  part  such  as  root,  tuber  or  seed, 
where  the  sugar  may  be  again  con- 
verted to  starch,  in  the  leucoplasts,  to 


Fig 


Starch 


remain  until  needed   by  the  plant  for  f /eC/onUlmiif.' ^  ^"'^ 
food.     Whereas    in   the  green  cells  of 
a  leaf  the  starch  does  not  ordinarilj^  accumulate  in  great 
quantities,  the  storage  cells  of  a  plant  become  so  packed 
with  it  sometimes  that  little  else  can  be  seen. 

Starch  is  a  carbohj^drate  and  is  closely  related  chemi- 
cally to  cellulose  and  to  the  sugars.  It  is  composed  of 
carbon,  hydrogen  and  oxygen  in  the  proportions  indi- 
cated by  the  formula  (C6Hio05)n,  in  which  ''n"  is  a 
fairly  high  Init  not  exactly  ascertained  amount.  By  the 
action  of  certain  organic  substances  produced  by  the  cell 
and  called  enzymes,  or  of  some  of  the  acids  and  heat,  it 
can  l)e  converted  into  some  forms  of  sugar. 

Starch  grains  frequently  show  a  concentric  structure, 


14  PROTOPLASM  AND  PLANT  CELLS 

due  apparently  to  the  successive  deposition  of  denser  and 
less  dense  la3'ers.  At  first  the  grains  are  entirely  en- 
closed by  the  plastid  but  as  they  increase  in  size  they 
become  excentrically  located  and  seem  eventually  to 
burst  out  of  the  plastid  at  one  side.  In  the  chloroplasts 
containing  pyrenoids  the  starch  grains  are  mostly  pro- 
duced in  intimate  connection  with  the  latter. 

24.  Aleuron.  In  the  dry  seeds  of  many  plants  there 
may  be  found,  sometimes  in  a  definite  layer  of  cells, 
sometimes  scattered  throughout  the  cells  of  the  seed, 
small  rounded  or  frequently  angular  granules  of  a  protein 
substance  called  aleuron.  This  is  stored  up  in  the  cells 
as  food  for  the  young  seedling.  These  aleuron  grains  are 
formed  in  small  vacuoles  in  the  cytoplasm,  the  aleuron 
being  in  solution  at  first  but  appearing  as  granules  or 
even  crystalloids  as  the  seed  loses  its  moisture  in  the 
process  of  ripening.  As  the  seed  absorbs  water  prepara- 
tory to  germinating  the  aleuron  goes  into  solution  again 
and  is  used  up  for  food.  Aleuron  is  frequently  found  in 
cells  containing  other  stored  up  food  matter  such  as 
starch  or  oil.  It  was  formerly  supposed  to  be  a  dry 
stage  of  protoplasm  but  is  now  recognized  as  one  of  the 
highly  complex  food  substances  out  of  which  protoplasm 
can  be  formed  by  the  cell. 

25.  Oils  or  Fats.  Many  plants  provide  for  the  use  of 
the  young  seedling  a  supply  of  fat  instead  of  starch. 
This  is  usually  present  in  the  cell  as  very  minute  drops, 
in  fact  almost  as  an  emulsion  throughout  the  cytoplasm. 
Sometimes  the  oil  droplets  are  of  considerable  size,  in 
very  oily  seeds  often  filling  all  the  interstices  of  the  cyto- 
plasm. Usually  these  fats  are  liquid  but  in  some  plants 
they  are  semisolids  of  the  consistency  of  butter.  They 
are  mostly  true  fats,  similar  to  those  found  in  animals, 


CRYSTALS  15 

but  in  some  plants  cells  are  found  which  contain  so-called 
''ethereal  oils,"  which  are  not  true  fats. 

26.  Crystals.  In  many  plants  may  be  found  cells 
containing  crystals.  These  may  be  cubical,  prismatic, 
regular  or  irregular  polyhedrons,  needles,  compound 
crystals,  etc.  Sometimes  the  cells  containing  them  are 
unchanged  but  often  they  are  enlarged  or  of  special 
shape.  This  is  especially  the  case  with  the  needle- 
shaped  crystals  which  are  called  raphids 
and  occur  in  large  bundles  in  the  cen- 
tral vacuole  of  rather  large,  thin-walled 
cells.  The  crystals  seem  to  be  formed 
by  the  cytoplasm,  in  which  they  occa- 
sionally lie,  or  more  frequently  in  special 
small  vacuoles  in  the  latter.     Eventu-  pound."  and  needTe^ 

,,  ,  r  1    •  ,  'XT,        shaped  crystals. 

ally  they  are  found  m  most  cases  m  the 

central  vacuole  in  which  some  of  them  may  have  had 

their  origin. 

27.  Crystals  in  most  plants  are  composed  of  calcium 
oxalate.  In  some  plants  calcium  carbonate  crystals 
occur,  while  crystals  of  still  different  composition  are 
occasionally  found.  The  purpose  of  crystals  is  not  clear 
in  all  cases  but  in  many  cases  they  are  probably  the 
product  of  the  combination  of  waste  substances  set  free 
in  the  course  of  some  of  the  important  chemical  pro- 
cesses of  which  the  cell  is  constantly  the  seat. 

Laboratory  Studies,  (a)  Make  a  thin  section  of  a  potato 
tuber.  Mount  in  water.  Note  the  large,  thin-walled  cells 
packed  with  numerous  ovoid,  concentrically  marked  starch 
grains.  Treat  with  iodine  solution.  The  starch  grains  become 
blue  or  purple.  In  very  young  tubers,  where  the  starch  grains 
are  not  so  large  nor  so  numerous,  they  may  be  seen  to  be 
enclosed  in  leucoplasts. 

(b)  Study  the  different  types  of  starch  grains  in  corn,  wheat, 
rice,  oats,  etc. 


16  PROTOPLASM  AND  PLAXT  CELLS 

(c)  Place  a  dish  of  water  containing  Spirogyra  in  the  light 
for  some  hours  and  then  examine  a  few  filaments.  In  the 
spirally  wound  chloroi)lasts,  around  the  pyrenoids  will  be 
found  masses  of  starch  which  become  more  evident  on  staining 
with  iodine. 

{(})  Make  thin  sections  through  various  leaves  that  have  been 
exposed  to  the  light  for  some  time,  staining  with  iodine.  In 
some  of  these  minute  grains  of  starch  will  be  found  in  the 
chloroplasts. 

(e)  Make  longitudinal  sections  of  ripened  apple  twigs,  in  the 
fall  or  winter  especially,  and  note  the  starch  stored  in  the 
rather  thick-walled  cells  of  the  pith. 

(/)  IMount  in  strong  alcohol  or  glycerine  a  thin  section  of  a 
pea  or  bean.  In  addition  to  starch  grains  the  cells  will  be 
found  to  contain  very  numerous  fine  granules.  Stain  with 
iodine.  These  small  aleuron  granules  will  be  stained  brown 
and  the  starch  blue.  To  another  section  apply  one  of  the 
tests  for  proteins  given  on  p.  9.  Mount  another  section  in 
water  and  note  the  effect  on  the  aleuron.  Examine  cotyle- 
dons of  germinated  peas  and  beans  for  presence  or  absence  of 
aleuron. 

(g)  Examine  a  cross-section  of  a  wlicat  grain.  The  aleuron 
will  be  found  in  a  layer  of  cells  outside  of  the  starch-containing 
cells.  This  laj^er  is  largely  removed  with  the  bran  in  the 
process  of  making  flour. 

(h)  Make  a  thin  section  of  a  seed  of  the  castor  oil  plant 
(Ricinus).  Mount  without  adding  water  or  any  other 
reagent.  Large  aleuron  grains  will  be  seen,  each  containing  an 
angular  protein  crystal  and  a  spherical,  so-called  "globoid,"  of 
inorganic  nature.  Add  a  little  water  and  some  of  the  oil  will 
escape  and  appear  at  the  edges  of  the  section  as  large  drops. 

(i)  Examine  various  oily  seeds  such  as  cotton,  flax,  peanut, 
or  an  oily  fruit  such  as  the  avocado  (Persea  gratissima)  or  olive. 
In  the  cells  w^ill  be  found  varying  amounts  of  oil.  By  treating 
the  sections  with  1  per  cent,  solution  of  osmic  acid  or  with 
alkannin  solution  the  oil  will  be  stained  respectively  black  or 
red. 

(j)  Make  a  thin  longitudinal  section  of  the  stem  of  spider- 
wort  (Tradescantia)  and  mount  in  water.  Certain  thin- 
walled  cells  will  be  found  containing  bundles  of  needle-shaped 
crystals  (raphids).     Many  of  these  will  be  torn  out  of  position 


CELL  SAP 


17 


and  scattered  throup;liout  the  si)cciinen.  These  crj'stals  are 
composed  of  calcium  oxalate.  Add  a  little  hydrochloric  acid 
and  they  will  dissolve  without  effervescence. 

(k)  Similar  crystals  may  be  found  in  many  other  plants, 
e.g.  Lidian  turnip  (Arisaema),  evening  primrose  (Oenothera), 
fuchsia,  garden  balsam  (Impatiens),  garden  rhulmrb,  etc. 

(/)  For  crystals  of  other  types  examine  sections  of  prickly 
pear  (Opuntia),  young  basswood  twigs,  scales  of  onion,  stem  of 
lamb's  quarters  (Chenopodium),  petiole  of  beet,  etc.  These 
are  also  composed  of  calcium  oxalate. 

(m)  Examine  a  thin  cross-section  of  the  leaf  of  the  rubber 
plant  (Ficus  elastica).  In  some  of  the  modified  epidermal 
cells  will  be  found  peculiar  stalked  crystalline  bodies  of  calcium 
carbonate  deposited  upon  a  cellulose  core  which  hangs  down 
into  the  cell  cavity  from  the  outer  jiortion  of  the  cell  wall. 
Treat  the  section  with, hydrochloric  acid.  The  cystolith,  as  it 
is  called,  dissolves  with  the  evolution  of  CO2,  leaving  the  cellu- 
lose core,  thus  distinguishing  it  from  calcium  oxalate,  which 
dissolves  without  effervescence. 


28.  Cell  Sap.  The  cytoplasm  of  a  cell  usually  contains 
a  large  amount  of  water  imbibed  by  it  but  not  really  a 
part  of  it.  Water  is  also  found  fre- 
quently in  drops  (vacuoles)  within 
the  cell.  This  is  the  cell  sap.  It 
holds  in  solution  the  various  soluble 
substances  absorbed  by  the  plant  as 
well  as  those  manufactured  by  the 
cell  itself.  It  makes  up  by  far  the 
greater  part  of  the  bulk  of  the  contents 
of  the  average  cell.  Among  the  sub- 
stances dissolved  in  the  cell  sap,  in 
addition  to  the  mineral  matters  absorl^ed  by  the  plant 
from  the  soil  water,  are  many  sorts  of  organic  compounds 
produced  by  the  cytoplasm.  The  most  important  of 
these  are  the  various  sugars  and  organic  acids.  The 
commonest  of  the  sugars  are  saccharose  or  cane  sugar 


Fu 


-Large  vacuoles. 


18  PROTOPLAS:^!  AND  PLANT  CELLS 

(C12H22O11),  glucose  or  grape  sugar  (C6H12O6),  fructose 
(CeHisOe),  etc. 

29.  Cane  sugar  is  found  in  great  quantities  in  the  cell 
sap  of  the  sugar  cane,  sugar  beet,  sugar  maple,  sorghum, 
Indian  corn  and  many  other  plants.  The  first  two  plants 
produce  the  bulk  of  the  sugar  of  commerce.  In  many- 
fruits,  such  as  grapes,  cherries,  gooseberries,  figs,  etc., 
glucose  is  present,  while  in  still  others,  e.g.  pineapple, 
peach,  plum,  strawberries,  etc.,  the  two  are  mixed. 
Fructose,  as  the  name  implies,  is  found  in  many  fruits, 
e.g.  the  grape.  In  many,  if  not  in  most  plants  glucose 
seems  to  be  the  form  in  which  green  cells  manufacture 
their  food,  storing  up  the  excess  over  immediate  consump- 
tion usually  as  starch,  from  which  it  is  again  obtained  as 
glucose.  Inulin  is  found  mostly  in  plants  of  the  sunflower 
family,  e.g.  sunflower  (Helianthus),  Dahlia,  elecampane 
(Inula),  etc. 

30.  The  organic  acids  found  in  the  cell  sap  may  occur 
in  acid  form,  but  frequently  are  found  as  acid  salts  of 
calcium  or  potassium  or  some  other  base.  The  most 
common  of  these  acids  are  maUc,  citric,  tartaric  and  ox- 
alic. They  seem  to  be  present  in  some  cases  as  food  for 
the  plant  while  in  others  they  doubtless  help  to  keep  the 
cell  turgid  by  raising  the  osmotic  pressure  within  the  cell 
to  the  proper  degree. 

31.  Among  the  substances  found  in  the  cell  sap  in  so- 
lution are  certain  compounds  known  as  alkaloids.  These 
are  perhaps  in  some  cases  products  of  the  breaking  down 
of  more  complex  substances  and  to  be  looked  on  as  a  sort 
of  excretion  product  comparable  to  urea  in  animals. 
However,  in  certain  plants  they  may  serve  as  reserve 
food  as  they  are  used  up  by  the  plant  if  no  other  food  is 
available.     They  are  nitrogenous  compounds  of  compli- 


FORMATION  OF  NEW  CELLS  19 

cated  composition,  usually  bitter  to  the  taste  and  very 
frequently  poisonous  to  animals. 

Laboratory  Studies,  (a)  To  show  the  large  amount  of 
water  in  living  cells  place  a  few  threads  of  pond-scum  (Spiro- 
gyra)  in  a  little  water  and  examine  under  the  microscope. 
Add  a  httle  strong  glycerine  which  has  a  great  avidity  for 
water.  Note  how  the  cells  collapse  as  the  water  is  withdrawn. 
Repeat  the  experiment  with  thin  sections  of  some  herbaceous 
stem  or  simply  allow  the  latter  to  dry  out  in  the  air. 

(b)  Taste  the  stem  of  sugar  cane  or  growing  Indian  corn  or  a 
piece  of  a  sugar  beet.  The  presence  of  sugar  is  readily  recog- 
nizable. Put  small  pieces  of  these  plants  into  considerable 
quantities  of  95  per  cent,  alcohol  to  remove  the  water,  or  into 
pure  glj^cerine.  The  water  is  withdrawn  rapidly  by  the 
reagents  and  the  cane  sugar,  which  is  practically  insoluble  in 
them,  crystallizes  out  in  fine  stellate  crystals  Sections  for 
examination  must  be  mounted  in  the  alcohol  or  glycerine  as 
water  will  redissolve  the  sugar. 

(c)  Make  thin  sections  of  the  root  of  Dahlia  or  sunflower 
(Helianthus)  that  has  been  preserved  in  strong  alcohol  and 
note  the  large  sphaerocrj'stals  of  inulin. 

(d)  To  study  glucose  or  fructose  test  the  juices  of  various 
fruits  with  Fehling's solution,  which  gives  a  precipitate  of  copper 
oxide  with  both  these  sugars  but  not  with  cane  sugar  or  inulin. 

(e)  The  presence  of  acids  or  acid  salts  is  readily  discernible 
by  the  taste  in  many  plants,  e.g.  stem  of  rhubarb,  leaves  of 
Oxalis,  fruit  of  lemon,  cranberry,  etc.  In  smaller  quantities 
it  can  be  demonstrated  by  placing  the  cut  surface  of  the  tissue 
to  be  tested  in  contact  with  a  piece  of  blue  litmus  paper  which 
will  be  turned  red  by  the  action  of  acids. 

32.  Formation  of  New  Cells.  No  cell  can  originate 
except  from  some  pre-existing  cell  or  cells.  IMost  cells 
are  capable  of  producing  new  cells  at  some  stage  of  their 
development,  but  frequently  the  power  is  soon  lost. 
New  cells  arise  either  through  the  division  of  a  cell  or 
through  the  union  of  two  (or  rarely  more)  cells.  In  the 
cell  formation  by  division  we  distinguish  two  types,  i>ac'h 


20 


PROTOPLASM  AND  PLANT  CELLS 


with  modifications,  \iz.,  fissioii,  in  which  the  cell  divides 
into  two  adjacent  parts  which  may  or  may  not  remain  at- 
tached, and  internal  cell  formation,  in  which  the  proto- 
plasm within  the  cell  divides  into  several  cells  which 
eventually  escape  from  the  old  cell  wall  as  naked  cells 
(zoospores  and  motile  gametes)  or  form  new  walls  for 
themselves  within  the  old  wall  and  bc^come  free  on  the 
rupture  or  decay  of  the  old  wall.  The  latter  type  in- 
cludes cases  in  which  all  the  protoplasm  is  used  up  in 
forming  the  new  cells,  as  in  zoospore  formation,  as  well 
as  those  in  which  only  a  part  is  so  used,  the  remainder 


W4 


til:::. 


Fig.  7. — Kuryokiucsis  (mitosis). 


lying  between  the  new  cells  and  the  old  wall,  as  in  the 
formation  of  ascospores  within  the  ascus.  Several  forms 
of  fission  may  be  distinguished.  The  commonest  type 
is  that  in  which  the  protoplasm  of  the  cell  separates 
into  two  parts  that  secrete  a  new  wall  between  them, 
the  new  cells  thus  remaining  attached  to  each  other. 
The  new  separating  wall  may  be  formed  as  a  ring-like 
thickening  on  the  old  wall  which  gradually  increases  in 


MITOSIS  (KARYOKINESIS)  21 

width  until  it  has  comi)h'ted  the  separation  of  the  two 
protopUismic  masses,  this  being  tlie  commoner  way  in 
the  lower  plants,  or  the  wall  may  be  produced  sim- 
ultaneously at  all  points  at  the  plane  of  separation  be- 
tween the  two  protoplasts,  as  is  the  case  in  most  higher 
plants.  In  some  of  the  lower  plants  the  whole  wall  be- 
gins to  constrict  at  the  middle,  giving  the  appearance  of 
pinching  the  cell  into  two  separate  cells  which  are  then 
free  from  one  another.  A  peculiar  type  of  fission  is  that 
termed  budding,  in  which  a  small  outgrowth  appears  at  a 
point  on  the  cell,  gradually  enlarging  until  it  is  as  large 
as  the  old  cell  and  then  l^ecoming  separated  from  it  by 
constriction  of  the  wall  at  the  point  of  emergence.  This 
is  especially  characteristic  of,  but  not  confined  to,  some  of 
the  yeasts. 

33.  Cell  division  is  in  most  cases  initiated  by,  or  more 
or  less  immediately  preceded  by,  the  division  of  the 
nucleus.  In  coenocytes,  on  the  contrary,  this  connection 
between  nuclear  division  and  that  of  the  coenocyte  seems 
to  be  lacking.  Two  types  of  nuclear  division  may  be 
distinguished,  direct  or  amitotic  and  indirect  or  mitotic. 
The  latter  process  is  generally  known  as  mitosis  or  karyo- 
kinesis.  The  direct  division  is  comparatively  rare  and 
appears  to  consist  of  a  simple  pinching  in  two  of  the  nu- 
cleus. By  far  the  commonest  method  is  that  of  mitosis. 
This  is  a  very  complicated  process  and  is  essentially  as 
follows,  ])eing  subject,  however,  to  many  more  or  less 
pronounced  variations  in  different  plants.  If  a  centro- 
some  is  present,  which  is  apparently  the  case  only  in  some 
of  the  lower  plants,  it  divides  into  two  centrosomes  which 
move  around  outside  the  nucleus  until  thej-  lie  at  oppo- 
site sides  in  a  line  at  right  angles  to  the  plane  of  division. 
The  nuclear  reticulum  now  begins  to  resolve  itself  into  a 
fine  tangled  thread  without  cross  connections,  the  chro- 


22  PROTOPLASJ^r  AND  PLANT  CELLS 

matin  granules  spreading  themselves  out  along  the  thread 
until  it  is  of  even  thickness.  The  thread  rapidly  shortens 
and  thickens,  eventually  becoming  a  thick,  more  or  less 
distinctly  spirally  arranged  thread  (spirem  stage).  At 
the  same  time  the  nucleolus  has  been  growing  smaller  or 
less  distinct  and  soon  disappears  entirely.  In  the  spirem 
thread  there  often  becomes  visible  at  this  stage  a  split  for 
its  whole  length.  However,  it  does  not  separate  along 
this  split  as  yet.  In  the  mean  time  outside  the  nucleus 
there  begin  to  appear  in  the  cytoplasm  immediately 
surrounding  the  centrosomes  fine  lines,  or  fibrillae  (of 
kinoplasm) ,  which  appear  to  center  at  the  centrosome  and 
extend  from  it  in  all  directions  but  especially  toward  the 
nucleus.  In  the  plants  which  have  no  centrosomes  there 
appear  near  the  poles  of  the  nucleus  tangled  masses  of 
fine  fibrillae  which  in  some  cases  form  a  sort  of  cap  at  each 
pole  or  even  may  entirely  surround  the  nucleus.  From 
this  tangled  mass  the  fibrillae  gradually  untangle  them- 
selves somewhat  and  finally  lie  in  the  form  of  a  cone  at 
each  pole,  with  the  apex  away  from  the  nucleus.  In  the 
forms  with  centrosomes  one  of  the  latter  lies  at  each  apex, 
often  surrounded  by  radiating  fibrillae  which  may  reach 
out  even  to  the  cell  wall.  Where  the  mass  of  fibrillae 
comes  in  contact  with  the  nucleus  the  nuclear  membrane 
disappears  and  soon  after  vanishes  at  all  other  points 
also.  The  fibrillae  push  into  the  nuclear  cavity.  In  the 
meanwhile  the  spirem  thread  breaks  transversely  into  a 
number  of  segments  called  chromosomes,  the  number 
being  constant  for  all  vegetative  nuclei  of  a  given  species 
of  plant.  Two  sets  of  kinoplasmic  fibrillae  can  now  be 
recognized.  Some  push  through  the  nuclear  cavity  until 
they  meet  and  unite  with  similar  ones  from  the  other  pole, 
forming  a  spindle-shaped  structure  commonly  spoken  of 
as  the  nuclear  spindle.     Other  sets  of  fibrillae  push  toward 


MITOSIS  (KARYOKINESIS)  23 

the  chromosomes  and  become  attached  to  them,  one  or 
more  sets  from  each  pole  being  fastened  to  each  chro- 
mosome. In  some  way,  perhaps  by  the  contraction  of 
these  fibrillae,  the  chromosomes  are  brought  to  he  at  the 
equator  of  the  spindle,  forming  the  so-called  equatorial 
plate.  The  chromosomes  are  of  various  shapes,  like  rods, 
or  resembling  the  letters  J,  V  or  U,  more  frequently  the 
last  two.  Usually  the  faint  longitudinal  split  which 
first  became  visible  during  the  spirem  stage  is  quite  dis- 
tinct. As  the  fibrillae  attached  to  the  chromosomes  con- 
tinue to  contract  the  latter  are  torn  in  two  along  the  line 
of  this  longitudinal  split,  one  half  being  dragged  toward 
each  pole.  When  these  daughter  chromosomes,  as  they 
are  called,  reach  the  two  poles  they  soon  join  to  each  other 
end  to  end  and  form  spirem  threads  similar  to  those 
formed  before  the  cleavage  into  chromosomes  (the  di- 
spirem  stage).  These  elongate  and  finally  form  a  long 
tangled  thread  along  which  the  chromatin  begins  to 
assemble  in  lumps  and  which  soon  forms  short  lateral 
connections  to  make  the  typical  nuclear  reticulum.  In 
the  meantime  the  nuclear  membrane  has  appeared 
around  each  daughter  nucleus  and  the  nucleolus  has  made 
its  appearance.  The  kinoplasmic  fibrillae  around  the 
centrosome  gradually  disappear  in  the  plants  with  cen- 
trosomes,  while  in  plants  without  centrosomes  they  dis- 
appear in  about  the  same  way  that  they  appeared,  or  in 
the  higher  plants  take  part  in  the  formation  of  the  sepa- 
rating membrane.  In  this  latter  case  the  spindle  fibrillae 
seem  to  increase  in  number  until  they  occupy  the  whole 
width  of  the  cell.  At  the  equatorial  plane  a  little  knot 
appears  on  each  fibrilla.  The  fibrillae  contract  and  as 
they  shorten  the  knots  increase  in  size  until  by  the  con- 
tact of  the  knots  with  each  other  a  thin  membrane  (of 
kinoplasm)  is  formed  which  separates  the  protoplasm  of 


24  PROTOPLASM  AND  PLANT  CELLS 

the  coll  into  two  parts.  This  membrane  splits  and  be- 
tween these  two  plasma  membranes  is  secreted  the  first 
layer  of  the  cell  wall  (middle  lamella).  It  is  of  interest 
to  note  that  mitotic  nuclear  division  is  essentially  the 
same  in  animals  and  plants.  In  the  former,  however, 
centrosomes  are  usually  present  while  they  are  lacking  in 
plants  except  in  some  of  the  lower  groups. 

34.  In  internal  cell  formation  the  nucleus  usually 
divides  several  times  before  the  cytoplasm  separates. 
Usually  the  new  cells  are  formed  almost  simultaneously 

in  this  case.  In  many  cases  the  cleavage  of 
the  cytoplasm  is  such  that  all  of  it  is  used  up 
in  forming  the  new  cells,  the  spindle  fibrillae 
taking  no  part  in  the  process.  In  other  cases, 
as  in  the  formation  of  ascospores  in  the  ascus, 
the  kinoplasmic  fibrillae  radiating  from  the 
Internal  c^  ccutrosomc  outlinc  the  new  cell  in  the  midst 

formation.  rj.i  i?j.i  i  '  ^        n 

01   the   mass  oi   cytoplasm,  leavmg  much  of 
the  latter  outside  of  the  new  cells,  the  so-called  cpiplasm. 

35.  Cell  formation  by  union  is  in  the  main  the  opposite 
process  to  that  by  division.  The  union  of  the  cytoplasm 
of  the  uniting  cells  is  usually  followed  by  the  union  of  the 
nuclei  to  form  one  nucleus.  If  the  cells  are  naked  the 
process  is  comparatively  simple,  but  when  enclosed  in 
walls  the  cells  must  either  escape  before  uniting,  or  open- 
ings must  be  made  in  the  walls  so  that  one  cell  can  pass 
into  the  other.  By  the  union  of  the  two  nuclei  the  num- 
ber of  chromosomes  is  doubled  and  remains  at  this  so- 
called  diploid  number  until  by  a  peculiar  modification  of 
the  mitotic  process  (the  reduction  division  ormeiosis)  the 
number  is  reduced  to  the  original  (or  haploid)  number. 

Laboratory  Studies,  (a)  Scrape  off,  after  moistening  with 
alcohol,  a  little  of  the  3'oung  white  moldy  growth  on  a  lilac 
leaf  (powder}'  mildew)  or  of  similar  mildews  on  cherry  shoots 


_  >EKrr  UBRARf 
IJ^  C.  State  College 


LABORATORY  STUDIES  25 

grass  leaves  or  other  plants.  Mount  in  dilute  potash. 
Threads  will  be  found  showing  the  formation  of  new  cells 
(spores)  l\v  fission. 

(b)  Add  a  little  sugar  (preferably  glucose)  to  a  little  potato 
water  (made  bj^  grating  up  a  raw  potato  and  heating  with 
water  to  extract  the  soluble  matter  and  filtering)  and  break  up 
in  it  part  of  a  yeast  cake  (''compressed  yeast")  setting  the 
solution  in  a  warm  place.  Examine  a  small  drop  of  the  scum 
or  sediment  after  a  few  hours  for  cells  showing  the  type  of 
fission  called  budding. 

(r)  By  growing  yeast  for  a  few  da3\s  on  a  moist  slab  of 
plaster-of-Paris  under  a  bell  jar  or,  less  successfully  in  many 
cases,  on  the  cut  surface  of  a  raw  potato  or  carrot  some  of  the 
cells  may  be  found  to  have  produced  four  cells  by  internal  cell 
division. 

(d)  Make  a  very  tliin  cross-section  through  a  young  flower 
bud,  or  moss  capsule.  In  the  stamens  of  the  former  or  in  the 
interior  of  the  latter,  if  they  are  at  the  right  stage,  will  be  found 
cells  which  have  divided  internally  into  four  parts  which  sub- 
sequently become  spores,  each  with  a  thick  wall  of  its  own. 

(e)  Take  a  flower  bud  of  Tradescantia  just  before  opening 
and  remove  a  stamen  and  mount  in  water  of  about  the  room 
temperature.  By  examining  with  proper  manipulation  of  the 
light,  some  cells  near  the  tips  of  the  stamen  hairs  may  be  found 
in  division  and  the  main  features  of  the  mitotic  division  of  the 
nucleus  may  be  dimly  seen. 

(/)  Examine  specially  prepared,  stained  sections  of  rapidly 
growing  root  tips,  stamens,  etc.,  where  cell  divisions  are  taking 
place  frequently.  Find  and  study  as  many  stages  as  possible 
of  the  mitotic  division  of  the  nucleus  and  cells.  These  prep- 
arations require  especial  technique  and  cannot  be  made 
successfull}^  by  the  beginning  student.  It  is  desirable  that  he 
study  good  preparations.  Such  can  be  obtained  of  various 
su})ply  houses  if  the  teacher  has  not  the  time  or  desire  to  make 
them. 

(g)  Cell  formation  by  union  can  be  observed  in  the  conjuga- 
tion of  pond  scums  (Spirogyra  or  Zygnema)  or  of  black  molds 
(Mucoraceae,  especially  Sporodinia,  which  is  frequent  on 
decaying  toadstools  and  can  be  transferred  to  bread  where  it 
grows  luxuriantly). 


26  PROTOPLASM  AND  PLANT  CELLS 

REFERENCE  BOOKS 

B.  AL  Davis,  Studies  on  the  Plant  Cell  (American  Naturalist, 

(1904-1905,  Boston). 
Strasburger,  Jost,    Schenck    and  Karsten,  Lehrhuch   der 

Botanik,  11  Ed.,  Jena,  1911  (or  English  Edition),  and  the 

12  German  Ed.  1913. 


CHAPTER  II 

THE  TISSUES  OF  PLANTS 

HISTOLOGY 

36.  In  many  groups  of  plants  a  single  cell  makes  up 
the  whole  plant.  In  such  groups  the  cells  may  vary 
considerably  in  different  species  but  there  is  not  possible 
a  differentiation  into  cells  of  different  structure  for  differ- 
ent functions.  All  of  the  normal  activities  of  the  plant 
are  carried  on  by  the  same  cell  and,  therefore,  the  modi- 
fications of  the  cell  are  limited  to  those  that  do  not  inter- 
fere with  any  of  these  functions.  Aside  from  these 
limitations  the  cell  may  vary  much  in  size,  shape,  struc- 
ture of  wall,  location  and  size  of  nucleus  and  vacuoles, 
etc. 

37.  In  other  forms  of  plants  there  are  several  to  many 
cells  forming  one  plant  in  which  all  of  the  cells  are 
essentially  alike  and  each  capable  of  continued  existence 
by  itself  even  if  the  others  should  be  destroyed.  Such  a 
plant  is  scarcely  more  than  a  group  of  nearly  independent 
individuals.  As  we  study  the  more  and  more  complex 
forms  of  plants,  however,  we  find  that  the  cells  are  no 
longer  all  alike  or  nearly  so,  but  that  some  are  different 
from  the  others  in  shape,  structure  and  function.  The 
cells  are  not  all  equivalent,  the  plant  is  not  now  a  collec- 
tion of  nearly  independent  individual  parts  (cells)  ))ut 
the  whole  must  be  considered  as  an  individual  made  up 
of  numerous  differentiated  parts.  It  is  true  that  in  the 
history  of  every  plant  there  occurs  a  one-celled  stage  and 

27 


28  THE  TISSUES  OF  PLANTS 

by  the  division  of  this  cell  the  plant  originates,  but  none- 
the-less  the  whole  plant  is  to  be  considered  as  a  unit  and 
not  as  an  association  of  distinct  cells. 

38.  In  such  higher  plants  we  can  distinguish  several 
types  of  differentiated  cells  and  can  with  correctness 
speak  of  tissues.  A  tissue  may  be  defined  as  an  associa- 
tion of  similar  cells  for  a  common  function.  In  the  less 
differentiated  plants  the  same  tissue  will  have  many 
different  functions;  in  the  more  highly  specialized  forms 
there  will  be  more  kinds  of  tissues  each  with  few^er  func- 
tions. In  the  study  of  tissues  we  must  distinguish 
between  the  so-called  ''false"  and  'Hrue"  tissues.  The 
former  are  those  that  are  formed  by  the  subsequent  close 
association  of  cells  that  originated  independently  of  one 
another.  Thus  many  separate  motile  cells  (zoospores) 
may  join  themselves  to  one  another  in  such  a  way  as  to 
form  a  definite  structure  (e.g.  Hydrodictyon)  or  a  sort  of 
tissue  may  be  formed  by  the  growing  together  of  numer- 
ous originally  separate  filaments  of  cells.  On  the  other 
hand  a  true  tissue  is  formed  by  successive  divisions  from 
one  or  a  few  cells,  so  that  every  cell  may  be  said  to  have 
been  formed  in  place.  In  the  false  tissues  the  walls 
between  adjacent  filaments  or  cells  of  different  origin  are 
double,  without  a  true  middle  lamella  while  in  true 
tissues  the  walls  are  single  and  the  middle  lamella  is 
present  (at  least  at  first).  It  is  sometimes  impossible  to 
make  a  very  sharp  distinction  between  these  two  kinds 
of  tissues  as  one  method  of  origin  may  be  combined  with 
the  other.  False  tissues  are  found  almost  exclusively 
in  the  higher  fungi  and  some  of  the  algae  while  the  tissues 
of  the  higher  plants  are  true  tissues. 

In  the  following  discussion  only  the  more  highly 
differentiated  types  of  tissues,  such  as  occur  in  the  higher 
plants,  will  be  described  in  their  main  features  while  the 


IVIERISTEM,  AND  PARENCHYMA  29 

loss  difTereiitiiited  or  more  gciKU'alized  tissues  of  the  lower 
plants  will  not  be  considered. 

39.  Meristem.  This  is  the  form  of  tissue  from  which 
ultimately  all  the  other  kinds  arise.  It  is  often  spoken 
of  as  rudimentary  tissue  from  this  fact.  It  consists  of 
small,  usually  rapidly  dividing  cells  (at  least  during;  the 
growing  season),  some  of  which  usually  continue  as 
meristem,  while  others  by  enlarging  and  ceasing  their 
active  division  and  by  other  modifications  become  other 
kinds  of  tissues.  Meristem  is  present  in  those  parts  of 
the  plant  where  new  cells  are  being  formed,  i.e.  in  young 
buds,  at  the  apex  of  growing  stems  and  roots,  in  the 
developing  seeds,  etc.  Meristem  cells  are  usually  small 
and  very  thin-walled,  and  filled  with  cytoplasm,  and 
with  a  nucleus  which  is  large  in  proportion  to  the  size  of 
the  cell  and  mostly  central  in  location. 
The  vacuoles  are  small  or  entirely  want- 
ing. At  the  growing  points  of  stems  and 
roots  the  cells  are  usually  nearly  cubical, 
in  other  locations  (e.g.  cambium)  they 
may  be  elongated.     If  the  plant  be  one  ^     «     ,,    . 

.   \         .         .  ,         ,  .  Fig.  9.— Moristem 

with  plastids  they  are  present  in  men-  tissue. 

stem  cells  often  as  a  single,  very  small,  hardly  distin- 
guishable body.  Some  botanists,  however,  are  of  the 
opinion  that  plastids  are  newly  formed  in  the  tissues 
developed  from  the  meristem. 

40.  Parenchyma.  This  is  the  chief  vegetative  tissue 
of  the  higher  i)lants  and  makes  up  much  the  larger  part 
of  the  living  portions  of  the  plant.  It  is  the  main  nutri- 
tive, storage  and  rei:)roductive  tissue.  Its  cells  are 
much  larger  than  those  of  meristem,  from  which  it  is 
directly  derived,  but  they  preserve  in  general  much  the 
same  shape,  i.e.  they  are  rounded  or  polyhedral  and  usually 
not  much    elongated.     The   cell  walls  are  thicker  than 


30  THE  TISSUES  OF  PLANTS 

in  meristem  but  are  still  usually  thin,  although  in  certain 
modifications,  e.g.  the  parenchyma  occurring  in  wood 
and  sometimes  that  in  the  pith  of  woody  twigs,  the  walls 
may  be  considerabl}-  thickened.  In  composition  the 
wall  is  usually  a  form  of  cellulose  except  where  thicken- 
ing has  begun  in  which  case  the  walls  are  often  lignified. 
A  large  vacuole  occupies  the  center  of  the  cell  and  leaves 
the  cytoplasm  as  a  thin  parietal  layer  (i.e.  lining  the  wall) 
although  there  are  often  cytoplasmic  strands  running 
across  the  cell  from  one  side  to  the  other  through  the 
vacuole.  The  nucleus  is  generally  imbedded  in  the 
parietal  cytoplasm  and  appears  relatively  small  owing 
to  the  great  increase  in  size  of  the  cell  in  its  development 
from  meristem,  unaccompanied  by  a  corresponding 
increase  in  the  size  of  the  nucleus.  The  chloroplasts  are 
well  developed  in  those  parenchyma  cells  exposed  to  the 
light  (except  of  course  in  plants  devoid  of  chlorophyll). 
Very  generally  at  the  angles  of  contact  of  three  or  more 
parenchyma  cells  the  middle  lamella  is  ruptured  or  dis- 
solved and  the  corner  of  each  cell  be- 
comes rounded  off  leaving  a  space 
which  becomes  filled  with  air,  a  so- 
called  intercellular  space,  these  form- 
ing a  continuous  aerating  system 
throughout  the  living  parts  of  the 
Fig.  10.— Parenchyma  plant.  lu  somo  parts  of  a  plant, 
as  in  the  pith,  the  parenchyma  cells 
die  early  and  the  cell  contents  disappear,  being  re- 
placed by  air.  Probably  this  occurs  by  the  absorption 
of  the  protoplasm  by  the  adjacent  cells. 

Laboratory  Studies,  (a)  For  undifferentiated  cells  examine 
the  one-celled  green  slime  plants  (Protococcus) found  as  a  green 
coating  on  the  north  side  of  trees  or  walls  and  the  manj^-celled 
pond  scums  (such  as  Spirogyra  or  Zygnema)  or  one  of  the  sim- 
ple filamentous  blue-green  algae  (as  Oscillatoria)  which  often 


LABORATORY  STUDIES  31 

forms    a    purplish  or  brown  slimy   layer  on   flower  pots  in 
greenhouses. 

(b)  For  false  tissues  examine  a  longitudinal  section  of  the 
stalk  of  a  toadstool.  Here  the  longitudinal  rows  of  cells  are 
distinct  filaments  grown  together  into  one  mass.  Similarly 
the  basal  portion  of  the  apothecium  of  cup-fungi  is  made  up  of 
false  tissue,  although  here  the  separate  filaments  are  often 
indistinguishable.  Some  of  the  algae  are  also  good  examples, 
e.g.  Udotea,  Lemanea,  Nemalion,  etc, 

(c)  For  meristem  examine  a  thin  longitudinal  section  of  a 
root  tip.  For  this  purpose  the  first  strong  root  from  a  ger- 
minating grain  of  Indian  corn  or  the  j^oung,  so-called  'Morace 
roots"  from  near  the  base  of  the  stem  of  that  plant  are  good,  as 
are  young  roots  from  onion  or  h3^acinth  bulbs.  By  staining 
lightly  with  eosin  or  safranin  the  nuclei  and  cytoplasm  become 
more  distinct. 

(d)  ]\Iake  similar  longitudinal  sections  of  a  very  young  flower- 
or  leaf-bud,  e.g.  lilac  or  elder,  or  of  the  growing  tip  of  asparagus 
or  of  a  pumpkin  or  squash  vine  and  examine  the  meristem  tis- 
sue. Compare  the  cells  with  those  in  corresponding  locations 
in  sections  made  in  the  older  parts  of  the  stem. 

(e)  For  parenchyma  cells  make  thin  longitudinal  and  cross- 
sections  of  a  young  green  stem  of  Indian  corn  or  of  a  green  shoot 
of  elder.  Excluding  the  woody  and  epidermal  parts  the  bulk 
of  the  stem  at  this  stage  consists  of  parenchyma.  Treat  the 
section  with  iodine  solution  and  then  with  sulphuric  acid.  A 
blue  coloration  indicates  cellulose. 

(f)  Make  a  cross-section  of  a  typical  leaf  such  as  apple,  lily, 
nasturtium,  etc.     The  green  cells  are  parenchyma  tissue. 

(g)  IMake  a  thin  section  of  the  tul^er  of  potato  to  show 
storage  parcncln^ma.  Similar  parenchyma  may  be  found  in 
the  fruit  of  an  apple  or  pear,  etc. 

(h)  In  thin  cross  or  tangential  sections  of  a  living  woody  twig 
will  be  found  the  medullary  ra3^s.  These  consist  of  rather  thick- 
walled  living  parenchyma,  the  walls  being  more  or  less  lignified 
and  provided  with  thin  spots  (pits)  here  and  there  through 
which  water  and  food  substances  can  pass  from  cell  to  cell. 
Stain  different  sections  with  iodine  and  sulphuric  acid  as  a  test 
for  cellulose,  and  with  a  five  percent  aqueous  solution  of  ])hlo- 
roglucin  and  hydrochloric  acid  as  a  test  for  lignified  cell  walls, 
the  latter  taking  a  red  coloration.     Examine  in  similar  manner 


32  THE  TISSUES  OF  PLANTS 

the  pith  cells  of  one  or  two  year  old  twigs  of  apple.     These  are 
also  somewhat  tliick-walled. 

41.  Sclerenchyma  is  the  name  given  to  a  tissue  con- 
sisting of  more  oi;  less  rounded  or  polyhedral,  usually 
not  much  elongated,  thick-walled  cells  whose  function  is 
to  give  support  or  protection  to  other  tissues.  These 
cells  originate  from  meristem  by  the  thickening  and 
lignification  of  the  walls,  passing  through  an  intermediate 
parenchymatous  stage.     During  the  process  numerous 

spots  on  the  walls  remain  thin  so  that 
eventually  they  show  as  canals  from  the 
small  central  lumen  of  the  cell  to  the 
original  outer  wall.    These  canals  or  pits 

Fig.  11. -Sclerenchyma    COrrCSpOUd     ITi     adjaCCnt      CClls.       Upon 

(  10  -ory  nut).  reaching  their  final  development  the  cell 
contents  die.  Sclerenchyma  cells  are  often  called  stone 
cells.  They  are  found  in  seed  coats,  nut  shells,  bark, 
etc.,  where  protection  or  support  is  required. 

42.  Of  a  much  different  type  from  the  foregoing  are 
those  tissues  consisting  of  elongated  cells  with  more  or 
less  thickened  walls  whose  function  is  the  mechanical 
strengthening  and  support  of  the  plant  body.  To  per- 
mit bending  while  at  the  same  time  retain- 
ing their  supporting  function  they  are  more 
or  less  elastic,  a  characteristic  less  marked 
in  the  short-celled  sclerenchyma  whose  func- 
tion is  protection  or  only  local  support.  ^^^^  12  — Coiien- 
We  can  distinguish  two  types  of  these  sup-  chyma. 
porting  or  mechanical  tissues,  collenchyma  and  fibrous 
tissue. 

43.  Collenchyma.  Directly  ])eneath  the  epidermis  of 
many  plants  are  found  smaller  or  larger  strands  of  elon- 
gated cells  whose  longitudinal  cell  walls  are  thickened  at 
the  angles  where  three  or  more  cells  come  in  contact. 


FIBROUS  TISSUE  33 

Except  in  old  cells  the  thickening  rarely  extends  out 
upon  the  wall  lying  between  the  angles.  The  cells 
remain  alive,  for  a  long  while,  and  usually  contain  chloro- 
plasts.  They  remain  capable  of  growth  longitudinally. 
Accordingly  collenchyma  is  found  to  be  the  chief  mechan- 
ical tissue  in  growing  parts  of  plants,  such  as  stems, 
leaf-stalks,  etc.  The  thickened  parts  of  the  walls  are 
composed  of  cellulose  and  transmit  the  light  with  a  pecu- 
liar pearly  luster  when  viewed  in  cross-section,  the  lumen 
of  the  cell  under  these  conditions  appearing  darker  than 
the  cell  walls. 

44.  Fibrous  tissue  consists  of  elongated  cells,  thick- 
ened on  all  sides,  usually  overlapping  at  their  more  or 
less  tapering,  often  pointed,  ends.  The  walls  show 
minute,  usually  ol^liquely  placed,  slit- 
like pits.  After  they  reach  full  develop- 
ment, the  cell  contents  die,  so  that  the 
cells  are  incapable  of  further  growth  or 
development.  The  thickened  walls  are 
usually  strongly  lignified.  In  cross-sec- 
tion the   cells  are  round  or  by  mutual  Fig.  13.— Wood  and 

,      1  -r-,.,  .  .  bast  cells. 

pressure,  angled.  Inbrous  tissue  is 
found  as  the  chief  mechanical  tissue  in  parts  of  plants 
which  have  completed  their  longitudinal  growth.  Two 
types  can  be  distinguished,  viz.,  bast  and  wood  fibers. 
The  former  are  located  in  the  outer  part  of  the  stem 
(in  the  cortex  in  the  Dicotyledoneae),  the  latter  in  the 
true  wood.  Bast  fibers  are  usually  longer  than  wood 
fibers,  and  more  slender,  with  often  thicker  but  less  com- 
pletely lignified  and  hence  more  elastict  walls.  Their 
usual  length  is  from  1  to  2  mm.  but  in  Bochmcria  nivea, 
the  ramie  plant  (according  to  Haberlandt)  they  reach  a 
length  of  220  mm.,  the  longest  plant  cells  known.  Wood 
fibers  are  usually  shorter  (mostly  0.3  to  3.1  mm.)  often 


34  THE  TISSUES  OF  PLANTS 

somewhat  thicker,  with  less  tapering  ends  and  frequently 
with  less  thickened  walls  which  are  more  strongly  ligni- 
fied  than  those  of  bast  fibers. 

Laboratory  Studies,  (a)  Break  tlie  shell  of  a  hickory  nut, 
ahnond,  coconut,  walnut,  peach-stone,  etc.,  and  after  smooth- 
ing the  broken  surface,  cut  off  a  thin  shaving,  using  a  pocket 
knife  or  scalpel  held  at  rather  an  oblique  angle.  Mount  in 
water  and  a  httle  potassium  hydrate.  The  very  small  cell 
cavities  show  connecting  pits  or  canals  radiating  from  them  to 
the  original  cell  wall  where  they  meet  similar  canals  from  the 
centers  of  adjoining  cells,  being  separated  only  by  the  thickness 
of  the  original  wall.  Concentric  markings  are  visible  in  the 
cell  walls  in  some  cases. 

(b)  Determine  whether  the  walls  in  sc^erenchyma  are  made 
of  cellulose  or  are  lignified,  by  testing  one  section  with  a  5  per 
cent,  aqueous  phloroglucin  solution  followed  by  hydrochloric  acid 
which  gives  a  red  color  for  lignified  walls,  and  another  section 
with  iodine  solution  followed  by  somewhat  diluted  sulphuric 
acid  which  gives  a  blue  color  for  cellulose  walls. 

(c)  Sclerenchj^ma  may  be  found  and  studied  (1)  as  the  little 
''grit"  bodies  in  the  flesh  of  the  pear  or  sapodilla  (Achras 
mpota),  (2)  in  the  underground  stem  of  the  brake  {Ptcridium 
aquilinimi),  (3)  next  to  the  epidermis  in  the  prickly  pear 
(Opuntia),  as  well  as  (4)  in  coats  of  many  seeds,  e.g.  apple, 
squash,  wild  cucumber,  and  (5)  forming  the  body  of  the 
seeds  of  many  palms,  e.g.  date. 

(d)  Examine  a  young  leaf-stalk  of  the  squash  or  pumpkin 
and  note  the  whitish  bands,  1  or  2  mm.  wide,  which  extend  from 
end  to  end  just  beneath  the  epidermis.  These  are  bands  of 
collenchyma.  They  may  be  readily  torn  out,  when  the  stalk 
will  be  found  to  have  lost  much  of  its  strength. 

(e)  Make  a  very  thin  cross-section  of  the  leaf-stalk  of  one  of 
the  foregoing  plants,  exactly  at  right  angles  to  the  axis  of  the 
collenchyma  strands,  and  examine  under  low  and  high  magnifi- 
cations. Test  with  iodine  and  sulphuric  acid  to  determine  the 
composition  of  the  walls. 

(/)  ]\Iake  longitudinal  sections  through  these  collenchyma 
Imnds.  If  good  sections  are  obtained  the  thickened  angles 
(becoming  thin  toward  the  point  where  the  thin  cross  walls 
occur),  chloroplasts  and  nuclei  will  be  found.     However,  only 


TRAClIEAllY  TISSUE  35 

those  cells  that  happen  to  be  so  placed  that  a  thickened  angle 
appears  in  the  section  will  show  this  feature.  On  the  other 
liand,  if  the  section  passes  between  the  corners  of  the  cell  the 
walls  will  appear  thin. 

(g)  CoUenchyma  may  be  found  also  in  the  young  green  shoots 
of  elder  (Sanibucus)  and  some  other  shrubs,  in  the  stems  of 
lamb's  quarters  (Chenopodium),  pigweed  (Amaranthus), 
petioles  of  beets  and  very  many  other  plants. 

(h)  Make  thin  longitudinal  sections  of  the  wood  and  bark  of 
the  basswood  (Tilia)  or  maj)le  (Acer)  and  macerate,  to 
separate  the  cells,  in  Schulze's  reagent  (i.e.  heat  in  a  test  tube  in 
nitric  acid  to  which  has  been  added  a  little  potassium  chlorate). 
Mount  a  bit  of  the  macerated  wood  section  on  a  slifle  and  tap 
the  cover  glass,  or  tease  the  section  apart  with  needles. 
Study  the  wood  fibers.  Do  the  same  for  the  bast  fibers  in  the 
bark. 

(i)  Now  make  thin  longitudinal  and  cross-sections  of  the 
same  kind  of  twig  without  macerating  and  study  the  fibers  in 
place  to  note  the  relation  of  the  overlapping  cells.  In  the  cross- 
section,  note  the  appearance  of  the  fibers  and  their  position  in 
the  twig. 

45.  Besides  the  foregoing,  there  is  a  group  of  tissues 
which  have  as  their  chief  function  the  conduction  of 
water  and  food,  the  so-called  conductive  tissues.  These 
are  of  three  kinds:  tracheary  tissue,  whose  primary  func- 
tion is  the  transportation  of  water,  and  sieve  and  lat- 
iciferous  tissues,  which  are  chiefly  concerned  with  the 
conduction  of  food  substances  manufactured  by  the 
leaves. 

46.  Tracheary  tissue  is  of  many  kinds.  The  term  is  hero 
used  to  include  those  elongated  cells,  whose  chief  function 
is  the  transport  or  storage  of  water.  The  lumen  is  usually 
rather  large  with  the  wall  thickened  in  a  more  or  less  regu- 
lar manner  to  give  strength.  At  the  same  time,  a  consider- 
able portion  of  the  wall  remains  thin,  permitting  the  en- 
trance or  exit  of  water.  The  cells  are  not  living,  i.e.  their 
protoplasm  dies  as  soon  as  they  have  attained  their  final 


36  THE  TISSUES  OF  PLANTS 

development,  so  that  the  conduction  of  the  water  is  not 
dependent  upon  the  activity  of  these  cells  but  occurs  in 
the  cavities  left  empty  by  the  disappearance  of  the  proto- 
plasm. Since  the  cells  lack  protoplasmic  contents  which 
would  furnish  the  turgor  to  keep  them  from  collapsing, 
the  thickening  of  the  walls  is  necessary.  It  often  happens 
that  adjoining  living  cells  swell  out  through  the  thinner 
places  into  these  cells,  these  bladder-like  projections 
being  called  tyloses.  A  distinction  is  made  between 
tracheids  which  are  formed  of  single  cells,  and  tracheae 
(singular,  trachea)  or  vessels,  which  are  more  or  less 
elongated  tubes  formed  by  the  absorption  of  the  cross 
walls  of  adjoining  cells  so  that  the  lumens  of  many  suc- 
cessive cells  are  all  connected.  The  latter  usually  attain 
the  greater  diameter.  Tracheids  are  mostly  not  over  1 
mm.  long  although  in  some  cases  they  reach  a  length  of 
1  centimeter  or  even  much  more.  Tracheae,  accord- 
ing to  Strasburger,  average  about  10  centimeters  long, 
but  in  some  cases  reach  a  length  of  2  to  even  5  meters. 
In  some  vines,  the  diameter  reaches  0.3-0.7  mm.  Trach- 
eary  tissue  is  found  only  in  the  higher  plants,  i.e.,  Seed 
Plants  and  Ferns  and  Fern  Allies. 

47.  In  accordance  with  the  character  of  the  thickening, 
there  may  be  distinguished  sev- 
eral types  of  tracheary  tissue, 
these  same  types  of  thickening 
being  found  both  in  tracheids 
l^^)Mg?"^r^  I  M  rn  ^^^  tracheae.  These  are  ringed 
^^ringtdTspirJureticJiatedK'^^   (or  anuular),  Spiral,  reticulated 

(netted),  scalariform  (ladder- 
like) and  pitted  tracheae  or  tracheids.  All  but  the  last 
are  named  after  the  manner  of  the  internal  thickenings  of 
the  walls.  The  pitted  cells,  however,  are  those  in  which 
the  thickening  is  more  extensive  than  in  the  others,  the 


TRACHEARY  TISSUE  37 

thin  places  remaining  only  as  small  pits.  The  cells  of  all 
these  structures  are  usually  more  or  less  pointed  and  over- 
lapping at  the  ends,  except  in  some  of  the  tracheae  in 
which  the  square  end  walls  were  dissolved  out.  They 
are  mostly  round  or  by  mutual  pressure  somewhat  angled 
in  cross-section. 

48.  The  spiral  and  annular  thickenings  are  the 
only  types  found  in  the  tracheary  tissue  that  is  formed  in 
stems  or  roots  that  are  still  elongating,  as  it  is  possible 
for  such  cells  to  elongate  by  the  stretching  or  growth  of 
the  unthickened  portion,  whereby  the  rings  become 
farther  apart  or  the  spirals  stretched  out  at  a  greater 
angle.  Very  often  adjacent  rings  may  be  connected  here 
and  there  by  a  spiral  or  the  same  vessel  may  have  annular 
thickenings  in  one  part  and  spiral  in  another.  There 
may  be  from  one  to  three  or  four  spirals.  The  reticu- 
late type  of  thickening  is  perhaps  to  be  considered  as  a 
many-spiraled  type  with  numerous  cross  connections 
from  one  spiral  to  the  next  so  as  to  form  a  network. 
Scalariform  vessels  are  usually  angular  in  cross-section 
and  have  their  thickenings  on  the  flat  faces  of  the  prisms 
as  horizontal  bars  connected  to  the  somewhat  thickened 
angles,  and  leaving  horizontally  elongated  thin  areas  be- 
tween them  like  the  openings  between  the  rungs  of  a 
ladder.  All  transitions  may  be  found  from  the  reticu- 
lated or  scalariform  structure  to  the  pitted  type.  The 
pitted  tissues  are  of  two  types:  (a)  with  simple  pits,  and 
(6)  with  bordered  pits.  In  the  first  the  pits  are  of  the 
same  diameter  through  their  whole  depth  or  even  wider 
toward  the  center  of  the  cell.  In  the  second,  the}-  are 
narrow,  adjacent  to  the  cell  lumen  and  are  much  wider  as 
they  approach  the  middle  of  the  cell  wall,  the  cavity  of 
each  pit  having  the  shape  of  a  planoconvex  lens.  The 
wall  or  diaphragm  separating  the  adjacent  pits  of  ad- 


38 


THE  TISSUES  OF  PLANTS 


xoi 


Fig.      15. — Tracheary     tissue 
(pitted  and  tracheids). 


joining  coUrf  is  very  thin  and  permeable  to  water  except 
a  button-like  thickening,  in  the  center.  When  seen  in 
surface  view,  a  bordered  pit  shows  a  double  circle,  the 
smaller  inner  one  being  the  opening  into  the  pit  and  the 
outer  circle,  the  outer  edge  of  the  diaphragm. 

49.  Special  mention  must  be  made  of  the  tracheids  of 
Conifers  (Spruces,  Pines,  etc.). 
These  are  shaped  and  thickened 
like  wood  fibers  but  differ  in 
possessing  on  their  radial  faces 
one  or  more  longitudinal  rows 
of  bordered  pits.  They  com- 
bine the  functions  of  tracheids 
and  fibrous  tissue,  serving  both 
for  conduction  of  water  and  for 
mechanical  support. 

50.  Sieve  Tissue.  In  almost 
all  of  the  higher  plants  and  in  many  of  the  more  massive 
lower  plants,  there  are  found  rows  of  elongated  rather 
wide  cells  whose  transverse  separating  walls  are  pierced 
by  numerous  larger  or  smaller  perforations.  Where  two 
such  cells  lie  side  by  side  parts  of  the  lat- 
eral separating  wall  will  often  show  simi- 
lar perforated  areas.  These  are  the  so- 
called  sieve  plates  which  give  the  name  to 
this  tissue.  The  walls  of  the  sieve  tubes, 
as  the  elongated  cells  are  called,  are  usu- 
ally rather  thin.  The  sieve  plates,  on  the 
contrary,  are  rather  thick.  In  surface  view 
they  look  like  a  sort  of  network.  In  some  cases,  the 
meshes  of  the  net  are  perforations,  in  others,  they  are 
thin  walled  areas  perforated  by  several  to  many  fine  holes. 
The  mature  sieve  tubes  have  the  walls  lined  with  a  thick 
layer  of  cytoplasm  in  which  the  nucleus   is   imbedded. 


Fig.   1G.— Sieve 
tissue. 


LACTICIFEROUS  TISSUE  39 

The  centi'iil  vacuole  is  filled  with  a  liquid  ver}-  rich  in  i)ro- 
tein  matter,  the  masses  of  this  protein  substance  often 
being  continuous  through  the  pores  of  the  sieve  plates 
with  those  of  the  adjoining  sieve  tubes. 

51.  The  sieve  tubes  of  the  Flowering  Plants  are 
accompanied  b}-  usually  slender  parenchyma  cells  full  of 
protoplasm,  the  so-called  companion  cells.  The  walls 
between  these  and  the  sieve  tubes  are  perforated  by 
numerous  very  minute  passages  invisible  except  b}"  special 
manipulation.  Other  forms  of  parenchyma  cells  are 
usually  found  adjacent  to  the  sieve  tissue.  The  function 
of  the  sieve  tissue  is  probably  the  transportation  of 
protein  substances  from  the  leaves  to  parts  of  the  plant 
where  they  are  needed  in  the  construction  of  new  cells. 
Possibly,  also,  sugars  are  transported,  at  least  in  part,  in 
the  same  tissues  as  well  as  in  the  ordinary  parenchyma 
cells  near  them.  The  function  of  the  companion  cells 
is  not  certain. 

52.  Laticiferous  Tissue.  This  consists  of  a  system 
of  tubes  extending  throughout  the  plant 
and  filled  wdth  a  substance  called  latex. 
This  is  usuall}'  white  (hence  the  name ''milk 
tissue"  often  applied  to  this  kind  of  tissue), 
but  may  be  colored  red,  j^ellow  or  even  be 
almost  clear  and  colorless.  The  latex  con- 
sists of  water  containing  usually  much  pro-  Fig.  i?.— Laticif- 

,,  erous  tissue. 

tem  matter  as  well  as  some  sugar  and 
salts  dissolved  in  it,  and  holding  in  suspension  numerous 
minute  globules  of  resin  or  in  many  cases,  caoutchouc. 
On  exposure  to  the  air,  the  latex  often  coagulates.  It  is 
from  the  latex  of  many  plants  that  rubber  and  gutta 
percha  are  obtained,  while  other  substances  of  great  value 
are  often  found  in  it  also,  e.g.  opium  in  the  latex  of 
the  poppy.     In  some  plants,  starch  grains  are  found  in 


40  THE  TISSUES  OF  PLANTS 

the  laticiferous  tubes.  The  walls  are  lined  with  cyto- 
plasm containing  nuclei.  They  are  mostly  thin  but  in 
Euphorbia  the  walls  are  thick  and  elastic. 

63.  Two  distinct  types  of  laticiferous  tissue  may  be 
distinguished:  (1)  Non-anastomosing  and  (2)  Anastomos- 
ing. The  forrner  consists  of  branching  tubes  which 
originated  from  single  cells  in  the  embryo.  These  cells 
elongate  and  branch,  keeping  pace  with  the  growth  of  the 
plant,  forcing  their  way  between  the  meristem  cells 
exactly  as  if  they  were  part  of  a  fungus  instead  of  a  tissue 
of  the  plant  in  which  they  occur.  They  appear  never  to 
anastomose.  They  are  found  in  the  Euphorbiaceae, 
Moraceae,  Apocynaceae,  etc.,  i.e.  in  the  chief  rubber- 
producing  families. 

54.  The  anastomosing  milk  vessels  are  formed  by 
the  fusion  (that  is  through  the  resorption  of  the  separat- 
ing walls)  of  adjacent  meristem  cells  in  such  a  way  as  to 
form  a  network  of  latex-bearing  tubes.  Short  lateral  out- 
growths may  also  be  sent  out  from  one  tube  to  another, 
thus  increasing  the  number  of  anastomoses.  Laticiferous 
tissue  of  this  type  is  found  especially  in  theLactucaceae, 
Papaveraceae,etc.,  as  well  as  in  a  few  of  the  Euphorbiaceae, 
e.g.  Manihot  and  Hevea,  both  rubber-producing  trees  of 
great  economic  value. 

Laboratory  Studies,  (a)  Make  a  thin  longitudinal  section 
of  the  stem  of  garden  balsam  (Impatiens)  or  any  other  her- 
baceous plant  that  has  not  begun  to  become  thickened  and 
wood3^  The  section  should  pass  through  one  of  the  vascular 
bundles.  There  will  be  found  various  tj^pes  of  tracheary 
tissue,  those  facing  the  interior  of  the  stem  being  usually  of  the 
annular  or  spiral  type,  with  reticulated  and  pitted  types  to- 
ward the  outside. 

(6)  Good  plants  for  study  are  Tradescantia,  especially  for 
ringed  and  spiral  types  of  tracheary  tissue;  Sida,  for  good  spiral 
and  reticulated  types;  Indian  corn,  pumpkin  or  squash,  etc., 
for  large  pitted  vessels. 


LABORATORY  STUDIES  41 

(<:•)  Study  tlie  foregoing  types  of  tracheary  tissue  in  cross- 
section  in  comparison  with  the  longitudinal  sections. 

((/)  The  larger  pores  in  the  wood  of  oak,  hickory,  etc.,  as 
well  as  in  the  grape,  are  pitted  vessels. 

(e)  Excellent  scalariform  vessels  are  to  be  found  in  the 
leaf-stalks  or  better  still,  in  the  underground  stems  of  the 
brake  {Ptcridium  aquilinum). 

(/)  The  tracheids  of  pine,  spruce,  etc.,  resembling  wood  fibers 
in  shape,  but  with  bordered  pits,  should  be  studied  by  making 
tangential  and  radial  longitudinal  sections  as  well  as  cross- 
sections  of  the  wood.  The  bordered  pits  occur  only  on  the 
radial  surfaces  of  the  tracheids. 

{g)  Spirally  marked  tracheids,  similar  in  shape  to  the  fore- 
going, may  be  found  in  the  wood  of  the  hackberry  (Celtis), 
and  ash. 

{h)  By  treating  various  kinds  of  wood  with  Schulze's  reagent 
(nitric  acid  and  potassium  chlorate,  warmed)  the  various  cells 
will  be  separated  and  the  tracheary  elements  of  different  kinds 
can  be  studied  separately. 

{%)  Sieve  tissue  is  easily  found  by  making  longitudinal  sec- 
tions of  the  stems  of  squashes  or  pumpkins  (Cucurbita)  or 
other  vines  such  as  grape,  clematis,  hop,  etc.  They  will  be 
found  in  the  part  of  the  vascular  bundle  Ij'ing  toward  the 
outside  of  the  stem  and  in  the  case  of  Cucurbita  also  on  the 
inner  side.  By  staining  with  eosin  or  carmine,  the  protoplasm 
and  protein  contents  will  be  stained.  If  alcoholic  material  be 
used,  the  contents  will  be  found  shrunken  away  from  the  sieve 
plates.  If  portions  of  living  stems  are  killed  before  sectioning 
by  dipping  into  very  hot  water,  the  protein  and  protoplasmic 
contents  will  be  coagulated  without  much  contraction. 

ij)  Make  numerous  very  thin  cross-sections  of  the  same 
stems  and  examine  until  sieve  plates  are  found  and  studied  in 
surface  view. 

{k)  Examine  a  drop  of  latex  from  milkweed,  spurge  or  poppy, 
under  high  magnification.  The  suspended  granules  will  be 
visible  as  fine  dark  brown  bodies  by  transmitted  light.  Test 
with  iodine  to  determine  whether  starch  grains  are  present. 

(/)  Collect  a  quantity  of  latex  of  spurge  (Euphorbia)  and 
let  it  evaporate  in  a  watch  glass.  The  residue  is  a  sticky, 
rubbery  mass,  which  on  being  burned,  has  the  characteristic 
odor  of  burning  rubber. 


42  THE  TISSUES  OF  PLANTS 

(m)  For  the  study  of  laticiferous  tissue  thin  tangential 
sections  are  best.  The  tissues  will  show  as  tubes  filled  with  a 
brown  granular  mass,  the  latex.  The  non-anastomosing  type 
can  be  found  in  the  milkweed  (Asclc})ias),  dogbane  (Apo- 
cynum),  and  spurge  (Euphorbia),  especially  the  more  fleshy 
forms  of  the  latter.  The  anastomosing  tyj^c  can  l)c  studied 
in  the  petioles  of  dandelion  or  lettuce,  or  in  the  stem  of  the 
poppy. 

(n)  The  long,  branching,  non-anastomosing  laticiferous  tubes 
of  Euphorbia  can  be  isolated  from  the  more  fleshy  leaved  sorts 
by  boiling  the  leaves  in  dilute  potash  solution  and  then  teasing 
out  a  piece  of  the  softened  tissues. 

(o)  To  examine  the  tissues  in  situ,  the  leaves  should  be 
placed  in  strong  alcohol  (90-95%)  for  some  hours.  If  the 
leaves  are  thick,  thin  sections  should  be  made  parallel  to 
the  surface.  These  sections,  or  the  whole  leaves  if  they  are 
thin,  should  then  be  placed  for  an  hour  or  so  in  a  clearing  fluid 
made  of  equal  parts  of  turpentine  and  carbolic  acid  (phenol). 
Mount  the  section  or  leaf  in  this  fluid.  The  tissues  are  made 
transparent,  and  the  laticiferous  tubes  filled  with  granules  of 
latex  can  be  studied  with  great  ease.  The  same  method  can  be 
used  for  studying  both  types  of  laticiferous  tissue. 

REFERENCE  BOOKS 

The  books  enumerated  for  Chapter  I  and  the  following. 
A.  DeBary,  Co?nparative  Anatomy  of  the  Vegetative  Organs  of 

Phanerogams  and  Ferns  (Engl.  Ed.  1884.  Oxford). 
G.    Haberlandt,    Physiologische    Pflanzenanatomie,    Leipzig, 

1904.     (Engl.  Ed.  1914.     London.) 


CHAPTER  III 

GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

HISTOLOGY 

65.  In  the  lower  plants,  where  all  cells  are  essentially 
alike  and  no  distinction  of  tissues  can  be  made,  we  often 
find  that  growth  takes  place  in  all  parts  of  the  plant,  al- 
most every  cell  being  capable  of  growth  and  division  at 
any  age.  In  many  plants,  however,  in  which  the  differ- 
entiation into  various  kinds  of  tissues  is  still  almost  lack- 
ing, we  find  that  growth  is  more  or  less  limited  to  certain 
regions  of  the  plant.  In  those  plants  where  the  tissue 
differentiation  is  strongly  marked,  we  find  that  the 
formation  of  new  parts,  as  well  as  growth,  is  localized 
in  groups  of  meristem  cells  at  the  apices  of  stems  and 
roots  (and  also  in  many  plants  at  the  nodes),  the  older 
cells  of  these  groups  gradually  changing  into  the  more 
permanent  tissues  of  the  plant. 

56.  In  many  seaweeds  and  fungi,  where  the  plant 
body  consists  of  separate  or  adjacent  rows  of  cells,  the 
terminal  cell  of  each  row  elongates  and  divides  by  a 
cross  partition  and  perhaps  division  occurs  in  one  or  two 
cells  behind  it.  Except  for  the  formation  of  branches, 
longitudinal  divisions  may  be  lacking  and  the  result  is 
only  the  formation  of  rows  of  cells. 

57.  In  the  plants  which  are  not  so  markedly  fila- 
mentous in  structure  the  new  tissue  at  the  ai)ex  may  arise 
by  the  division  of  a  single  aj)ical  cell.  This  division 
may   be   by   horizontal   i)artitions,    the   seguKMits    thus 

43 


44     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

formed  dividing  subsequently  by  both  horizontal  and 
longitudinal  partitions  (as  in  Sphacelaria  and  many  other 
algae).  More  often,  we  find  that  the  apical  cell  is  a  three 
sided  pyramid,  the  convex  base  of  the  pyramid  being 
the  apex  of  the  shoot.  Successive  cells  are  cut  off  from 
the  three  sides  and  the  segments 
thus  produced  divide  by  various 
partitions  so  as  to  produce  the  mass 
of  meristem  cells  from  which  the  tis- 
,„     .  .    ,    „    r    sues  become  differentiated.    Some- 

FiG.   18. — Apical  cells  of  ,  , 

a    seaweed    (Sphacelaria),       timeS,      mstcad      of     the     apiCal     Cell 

and  a  moss.  .  ^      , 

cuttmg  off  three  rows  of  segments, 
it  produces  only  two  or  in  other  cases,  four. 

58.  In  most  of  the  Flowering  Plants,  a  group  of  cells 
is  found  at  the  apex  of  the  stem  or  root  instead  of  one 
cell,  these  giving  rise,  by  their  division,  to  the  mass  of 
meristem.  This  group  of  apical  cells,  or  the  single  apical 
cell  with  the  cells  derived  from  it,  is  called  the  growing 
point. 

59.  We  can  usually  distinguish  three  different  tissue 
regions  at  or  a  short  distance  back  from  the  growing 
point  of  higher  plants.  At  the  outside  we  find  a  single 
layer,  the  epidermis,  which  consists  of  cells  that  divide 
only  by  walls  perpendicular  to  the  surface.  When  this 
layer  has  an  initial  cell  or  cells  distinct  from  the  inner 
layers  the  portion  near  the  apex  is  often  spoken  of  as 
the  dermatogen.  The  next  region  is  spoken  of  as  peri- 
blem,  and  may  consist  of  one  or  several  layers  of  cells 
surrounding  the  centrally  located  plerome.  These  two 
regions  may  have  separate  sets  of  apical  cells  or  the  dis- 
tinction may  occur  only  some  distance  from  the  apex. 
In  most  roots,  the  apex  is  covered  by  the  root  cap,  a 
mass  of  cells  produced  by  the  periclinal  division  (i.e. 
by  walls  parallel  to  the  surface)  of  a  layer  of  cells  outside 


GROWING  POINT  45 

of  the  dermatogen,  or  in  some  cases,  of  the  dermatogen 
itself,  or,  in  still  other  cases,  by  the  division  of  some  of 
the  cells  of  a  common  mass  of  initial  cells  from  which  the 
root  cap  as  well  as  epidermis,  periblem  and  plcrome 
arise.  On  the  growing  points  of  stems,  the  new  branches 
arise  by  the  formation  of  secondary  growing  points  at 
the  side  of  the  main  one,  these  having  the  same 
general  plan.  Those  that  produce  the  leaves  often  grow 
faster  than  the  mai  growing  point  and  sur- 
round and  protect  it,  thus  forming  a  bud.  v  ^      .■ 

60.  As  the  growing  point  progresses,  the 
cells  formed  in  it  come  to  lie  further  and 
further  from  the  apex.  They  increase  in  size  V,: 
and,  after  a  while,  cease  to  divide.  Certain  v.>'' 
of  the  cells  remain  meristematic  a  long  while;  DfrmatigeiT 
others  become  elongated,  i.e.  cease  early  to  di-  pYe*i-^o  m  Tit 
vide  transversely,  and  eventually  become  ering  Pialr" 
transformed  into  fibrous,  tracheary,  sieve  tis- 
sue or  collenchyma.  Some  cells  merely  enlarge  and 
become  parenchyma.  Thus,  near  the  tip  the  cells  will 
be  found  to  be  all  meristematic,  but  further  back,  various 
kinds  of  tissues  may  be  found. 

Laboratory  Studies,  (a)  Make  a  longitudinal  section  of  the 
end  of  a  Ijranch  of  the  marine  alga,  Codium  tojuentosinn.  Here 
the  growing  region  is  not  a  few  cells  as  in  a  true  growing  point, 
but  each  filament  elongates  at  the  aj)cx  without  tlie  production 
of  cross  walls.  Many  of  the  Red  Seaweeds  (Rliodophyceae) 
show  the  same  type  of  apical  growth  except  that  transverse 
walls  are  formed  near  the  apex  of  each  filament  (e.g.  Melobesia, 
Ncmalion,  etc.). 

(b)  Examine  the  end  of  a  shoot  of  Sphacelaria,  one  of  the 
Brown  Seaweeds.  Here  there  is  a  single  ajiical  cell  which  divides 
by  a  transverse  partition,  the  segments  tluis  formed  dividing 
longitudinally  and  transversely. 

{(■)  Make  a  thin  longitudinal  section  througli  the  growing 
point  of  a  moss  or  of  a  stem  or  root  of  a  fern  or  horsetail 


46     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

(Equisetum).  This  is  a  difficult  section  to  make,  but  if  suc- 
cessful the  growing  point,  with  its  single  apical  cell,  can  be 
studied.  Sometimes  this  can  be  seen  better  by  making 
successive,  very  thin  cross-sections  at  the  tip  of  a  fern  root. 
In  this  case,  the  apical  cell  will  be  seen  in  transverse  view. 

((/)  IVIake  a  longitudinal  median  section  through  the  growing 
points  of  a  stem  and  a  root  of  a  Flowering  Plant.  (Stained 
microtome  sections  are  preferable  to  hand  sections  since  they 
are  thinner  and  more  likely  to  show  the  desired  features.) 
Note  that  all  of  the  tissue  near  the  tip  is  meristem.  Observe 
the  three  regions,  dermatogen  (epidermis),  periblem  and 
plerome.  Trace  them  to  their  origin.  On  the  root  section, 
note  also  the  root  cap  and  its  origin. 

61.  The  tissues  produced  from  the  primary  meristem 
in  the  manner  described  above  have  definite  functions 
to  perform,  and  occupy  definite  positions  in  the  plant 
body.  The  outer  layer  or  epidermis  is  set  off  as  a  boun- 
dary tissue;  other  cells  are  developed  into  the  skeletal  or 
supporting  tissues,  still  others  are  for  transportation  of 
water  and  food,  while  the  remainder  of  the  cells  are  at 
first  not  so  clearly  differentiated  for  special  functions. 
This  less  differentiated  group  of  tissues  may  eventually 
fulfill  various  functions  depending  upon  the  part  of  the 
plant  they  occupy,  the  nature  of  the  plant,  etc.  Thus 
they  may  be  food  making,  as  in  leaves;  for  storage  pur- 
poses, as  in  tubers,  many  roots,  some  pith,  etc. ;  protective, 
as  in  the  shell  of  nuts  where  the  tissue  is  changed  to 
sclerenchyma. 

62.  According  to  the  kinds  of  tissues  and  functions, 
it  is  customary  to  differentiate  several  so-called ''tissue 
systems.''  These  may  be  defined  as  aggregations  of 
elementary  tissues,  forming  definite  portions  of  the  plant 
and  with  a  definite  function.  It  is  at  once  evident 
that  tissue  systems  cannot  be  distinguished  where  tissues 
are  not  yet  differentiated.  In  fact,  we  usually  speak  of 
them  only  in  connection  with  the  higher  plants. 


EPIDER.MAL  8\\STEM  47 

63.  Three  tissue  systems  are  easily  recognizable  in 
the  higher  plants  apart  from  the  less  differentiated  mass 
of  cells  in  which  they  lie.  These  are:  (1)  the  epidermal 
system,  composed  mainly  of  the  boundary  cells  and  their 
appendages  (hairs,  scales,  stomata,  etc.) ;  (2)  the  conducting 
system,  comprising  those  tissues  which  are  water  or 
food  conducting  and  the  tissues  immediately  associated 
with  these;  and  (3)  the  mechanical  or  skeletal  system, 
consisting  of  the  fibrous  tissue,  collenchyma  and  scler- 
enchj^ma  which  furnish  the  rigidity  and  strength 
necessary  for  the  plant.  The  latter  two  are  sometimes 
considered  together  as  the  fibrovascular  system,  while 
the  remaining  tissues  are  often  grouped  under  the  name 
fundamental  system.  The  latter  is,  however,  no  definite 
aggregation  of  tissues  but  rather  the  residue  of  less 
strongly  specialized  tissues  from  which  we  have  rather 
arbitrarily  set  off  the  other  tissue  systems,  for  we  must 
remember  that  these  are  all  coherent  parts  of  one  plant 
body  and  not  separate  parts  without  close  interrelation. 

64.  The  Epidermal  System  of  Tissues.  This  is 
perhaps  the  earliest  tissue  system  to  have  been  differ- 
entiated from  the  remainder  of  the  plant.  In  many 
lower  plants,  the  exterior  and  interior  cells  show  no 
visible  differences,  but  even  here  among  some  we 
find  that  the  outer  cells  are  more  closely  crowded  together 
and  smaller  while  the  inner  cells  are  loosely  arranged. 
In  the  fruits  of  some  fungi,  the  outer  layers  of  cells  are 
firm  and  resistant.  Some  of  the  Liverworts  and  ^Mosses 
possess  an  outer  layer  of  cells  distinct  from  the  inner 
cells  and  evidently  of  protective  nature.  It  is  only  in 
the  higher,  more  massive  land  plants,  however,  that  we 
find  a  really  distinct  epidermal  system  of  tissues.  Thus 
in  the  Ferns  and  onward  through  the  various  Fern  Allies 
and  throughout  the  Seed  Plants,   the  epidermis  and  its 


48     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 


appendages  are  well  developed.  It  is  worthy  of  note, 
however,  that  those  plants  of  these  groups  that  have 
reassumed  the  aquatic  habit  have  their  epidermis  scarcely 
distinguishable  from  the  rest  of  the  tissues.  The  roots 
of  most  plants,  being  usually  in  moist  soil,  have  their 
epidermis  not  very  strongly  differentiated. 

65.  The  Epidermis.  In  most  cases  the  epidermis 
consists  of  a  single  outside  layer  of  cells  which  surrounds 
the  whole  plant  in  an  almost  uninterrupted  sheet.  It 
frequently  originates  from  an  apical  cell  or  group  of  cells 

distinct  from  those  producing  the 
rest  of  the  tissues,  or  is  differen- 
tiated from  the  latter  near  to  the 
growing  point.  Mostly  the  epider- 
mal cells  may  be  considered  as  a 
special  kind  of  parenchyma  tissue 
with  a  protective  function.  In 
many  plants,  however,  especially 
those  of  hot,  dry  climates,  the  cells 
soon  become  thickened  and  more 
or  less  sclerenchymatous.  Usually 
they  remain  alive,  but  in  the  forms  where  they  have 
been  changed  to  sclerenchyma  the  contents  commonly 
die.  In  most  cases,  epidermal  cells  show  no  well  de- 
veloped chloroplasts  although  the  cell  sap  may  be  brightly 
colored. 

66.  In  shape,  the  epidermal  cells  are  usually  more  or 
less  flattened  parallel  to  the  surface  of  the  plant.  If 
the  growth  of  the  organ  is  nearly  equal  in  length  and 
width,  the  epidermal  cells  seen  from  the  outside  will  be 
nearly  isodiametric,  but  if  the  longitudinal  growth  has 
been  markedly  greater  than  the  transverse  growth,  the 
epidermal  cells  will  usually  be  elongated.  Frequently 
the  cells  are  very  irregular  in  outline.     Except  for  the 


Fig. 


20. — Epidermis,   with 
stomata. 


EPIDEILMIS  49 

stomata,   to  be   described  later,  no  openings  occur  be- 
tween the  cells,  even  at  their  angles. 

67.  The  most  characteristic  feature  of  well  developed 
epidermis  cells  is  the  thickening  of  the  external  wall 
and  the  deposition  in  the  outer  layers  of  this  wall  of  a 
waxy  or  fatty  substance  called  cutin.  This  water-proofs 
the  walls  to  a  large  extent  and  prevents  loss  of  water 
through  them  by  evaporation.  The  cutin  is  not  de- 
posited equally  throughout  the  outer  wall,  but  is  least 
toward  the  cell  cavity  and  greatest  at  the  outside.  The 
outer,  strongly  cutinized  portion  of  the  wall  is  often 
very  distinct  in  appearance  from  the  remainder  of  the 
wall  and  can  sometimes  be  stripped  off  as  a  continuous 
sheet,  the  cuticle.  Often  this  is  coated  externally  with 
a  waxy  or  resinous  coating,  the  ''bloom"  of  some 
leaves  or  fruits. 

68.  The  cutinized  layer  extends,  in  many  cases,  not 
merely  over  the  outer  surface  of  the  cell  wall  but  even 
down  between  the  adjacent  cells  for  some  distance. 
In  roots,  on  the  other  hand,  the  younger  parts  are  not  at 
all  cutinized  and  further  from  the  tip  the  cutinization  is 
only  comparatively  slight.  The  root  hairs  are  cutinized, 
if  at  all,  only  in  their  basal  portion. 

69.  While  the  epidermis  always  consists  at  first  of 
but  one  lixyev  of  cells  it  becomes  two  to  four  layered  in 
some  plants,  e.g.  oleander  {Nerium  oleander),  rubber 
plant  {Ficus  elastica),  various  cactuses  (Opuntia),  etc., 
by  subsequent  periclinal  division  (i.e.  division  by  the 
formation  of  a  cell  wall  parallel  to  the  outer  surface) 
of  the  original  layer.  The  outer  walls  of  these  new 
layers  may  become  cutinized  successively,  from  the 
outer  toward  the  inner  layers. 

70.  The  hairs  originate  mostly  as  outgrowths  of  single 
epidermal  cells.     In  the  case  of  young  roots  the  epidermal 

4 


50     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

cells  at  a  distance  of  a  few  millimeters  from  the  tip  grow 
out  into  long,  normally  unbranched,  thin-walled  hairs, 
whose  lumen  is  continuous  with  that  of  the  main  body 
of  the  cell.  These  root  hairs  are  not  cutinized,  or  only 
so  at  the  base.  They  may  attain  a  length  of  two  or  three 
centimeters  but  are  mostly  not  over  one  centimeter  in 
length  and  often  much  less.  The  thin  wall  is  lined  by  a 
delicate  layer  of  cytoplasm  and  the  central  vacuole  is 
very  large.  These  hairs  push  in  between  the  particles 
of  soil  and  lie  in  the  film  of  water  with  which  these  are 
covered,  absorbing  some  of  this  water  by  osmotic  action. 

Such  mineral  salts  as  are  in 
solution  in  this  soil  water  in 
greater  concentration  than 
that  of  the  same  salts  in  the 
cell  sap  diffuse  into   the  cell 

Fig.  21.— Root  hair,  glandular  hair,    and  Upward  thrOUgh  the  plant 
branched  hair,  hair  of  nettle.  ,  _  ,  i  i 

except   so  far  as  the  plasma 
membrane  is  impermeable  to  them. 

71.  The  hairs  on  those  parts  of  the  plant  exposed  to  the 
air  may  be  continuous  with  the  epidermal  cells  from 
which  they  have  arisen,  but  mostly  are  separated  from 
them  by  cross  partitions.  They  may  remain  one-celled 
or  may  become  many  celled  by  cross  septa.  Sometimes 
they  are  much  branched  or  merely  bifid  or  stellately 
divided.  In  some  cases  the  end  cell  of  a  short  hair 
divides  by  vertical  partitions  in  several  planes  to  form  a 
shield-shaped  structure.  Some  hairs  have  the  terminal 
cell  enlarged  and  functioning  as  a  gland  which  secretes 
sticky  or  oily  substances.  Certain  hairs  (as  those  of 
nettles)  contain  strong  irritant  poisons.  The  tip  of  the 
hair  penetrates  the  skin  of  animals  coming  in  contact  with 
the  plant  and  then  breaks,  permitting  the  poison  to  be 
forced  out  into  the  skin. 


HAIRS,  AND  STOMATA  51 

72.  Not  to  be  confused  with  hairs  are  those  outgrowths 
called  emergences.  These  are  not  epidermal  in  nature 
but  are  projections  produced  ])y  the  develo]:>ment  of 
cells  beneath  the  epidermis.  Often  such  emergences 
are  found  bearing,  and  as  it  were,  forming  the  support 
for  a  stout  hair,  as  in  the  sunflower  or  nettle. 

73.  The  presence  of  hairs  seems  to  be  advantageous 
to  plants  in  many  ways.  They  make  it  difficult  for  small 
insects  to  ascend  the  plant,  especially  if  the  hairs  are 
pointed  downward  or  are  sticky-glandular.  Stinging 
hairs  like  those  of  the  nettle,  and  also  merely  sharp- 
pointed  stiff  hairs,  such  as  abound  on  many  plants, 
are  deterrents  for  animals  that  would  otlierwise  feed 
on  the  plant.  The  same  is  probably  true  of  various 
evil-smelling  substances  secreted  by  some  glandular 
hairs.  Finally,  it  has  been  shown  that  the  presence  of 
hairs  and  scales  reduces  the  loss  of  water  from  the  plant 
by  forming  an  entanglement  for  a  layer  of  air,  thus 
preventing  the  air  currents  from  coming  into  direct 
contact  with  the  epidermis. 

74.  Stomata  (singular,  stoma),  or  breathing  pores, 
are  definite  openings  through  the  epidermis  to  air 
cavities  beneath,  through  which  an  exchange  of  gases 
takes  place.  These  cavities  (''substomatal  chambers") 
are  connected  with  the  intercel- 
lular air  spaces  throughout  the 
plant. 

75.  Except  in  the  Liverworts 
(Hepaticae),  where  the  stomata 
are   of   different    structure,    the 

typical  stoma  consists  of  an  0]:)en-    Fig.  22.— Stomata,  surface  and 

crosa-scctiou. 

ing,  slit-shaped  or  narrowly  elli])- 

tical,  bordered  by  two,  usually  ('hlur()j)liyll-l)(niring,  e])i- 

dermal  cells, somewhat  kidney-shaped,  and  iiicontact  with 


52     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

each  other  at  both  ends.  When  these  guard  cells  become 
more  turgid  they  curve  outward,  thus  opening  the  stoma, 
while  a  loss  of  turgidity  results  in  its  closure.  Usually 
the  stomata  open  while  the  plant  is  in  the  light  and  close 
partly,  sometimes  completel}^,  in  darkness.  An  excessive 
loss  of  water  by  the  plant  reduces  the  turgor  of  the  guard 
cells,  overcoming  the  effect  light  has  in  opening  the 
stomata,  and  causes  them  to  close,  thus  conserving  the 
moisture  in  the  plant. 

76.  Stomata  occur  on  aerial  leaves  and  stems  and 
more  rarely  on  flowers  and  fruits.  On  underground  stems 
and  leaves  they  are  less  abundant  (and  often  not  func- 
tional), Avhile  they  are  wanting  on  roots.  On  submerged 
parts  of  aquatic  higher  plants  they  are  lacking  or  only 
rudimentary.  On  leaves  they  are  usually  more  abundant 
on  the  lower  than  on  the  upper  surface.  The  numbers 
as  well  as  size  of  the  stomata  vary  greatly  for  different 
species.  The  following  table  will  give  an  idea  of  their 
relative  abundance  in  some  plants.     (Page  53.) 

Laboratory  Studies,  (a)  Strip  off  the  epidermis  from  the 
upper  and  lower  surfaces  of  the  leaves  of  various  plants,  and 
mount  with  the  outer  surface  upward.  If  air  bubbles 
interfere,  add  alcohol,  and  follow  this  by  a  weak  potash 
solution,  to  swell  the  tissues  again.  Leaves  of  various  grasses 
or  of  carnation  will  show  epidermal  cells  much  elongated,  while 
more  isodiametric  cells  may  be  found  on  the  leaves  of  such 
plants  as  the  live-for-ever  (Sedum  or  Sempervivum),  dock 
(Rumex),  cabbage,  etc. 

(b)  In  the  same  specimens  that  were  used  for  the  foregoing, 
study  the  stomata  and  their  relations  to  the  adjacent  cells. 
Compare  the  numbers  of  stomata  on  the  two  sides  of  the  leaf, 
and  their  relative  size  and  number  on  different  species  of  plants. 

(c)  Cut  cross-sections  of  various  leaves.  Those  of  cabbage 
and  carnation,  as  well  as  of  many  other  plants  that  grow  in  dry 
regions,  will  show  a  considerable  development  of  cuticle.  Note 
the  structure  of  the  stomata  as  shown  in  cross-section,  and  their 


NUM15ER  OF  STO.MATA 


53 


Olive,  Olea  europaca 

Black  Walnut,  Ju<>;laiis  nigra 

Red  Clover,  Trifoliuni  pratense 

Lilac,  Syringa  vulgaris 

Sunflower,  Helianthus  annuus 

Cabbage,  Brassica  oleracea 

Sycamore,  Platanus  occidentalis 

Lombardy  Poplar,  Populus  nigra  italica. 

Hop,  Huniulus  lupulus 

Plum,  Prunus  domestica 

Apple,  JMalus  malus 

Barberry,  Berberis  vulgaris 

Pea,  Pisum  sativum 

Box,  Buxus  sempervirens 

Cherry,  Prunus  mahaleb 

Thorn  Apple,  Datura  stramonium 

Indian  Corn,  Zea  maj^s 

Cottonwood,  Populus  deltoides 

Wind  Flower,  Anemone  nemorosa 

Lily,  Lilium  bul])iferum 

Iris,  Iris  germanica 

Oats,  Avena  sativa 

House  leek,  Sempervivum  tcctorum 

Water  Lily,  Castalia  lotos 


In  one 

square 

millimeter 

Upper 

Lower 

side 

side 

0 

625 

0 

461 

207 

335 

0 

330 

175 

325 

138 

302 

0 

278 

55 

270 

0 

256 

0 

253 

0 

246 

0 

229 

101 

216 

0 

208 

0 

204 

114 

189 

94 

158 

89 

131 

0 

67 

0 

62 

65 

58 

48 

27 

11 

14 

G25 

0 

relation  to  the  substomatal   chambers   and  the  inter-cellular 
spaces  of  the  leaves. 

(d)  Make  a  cross-section  of  the  leaf  of  oleander  {Xcrium 
oleander)  or  rubber  plant  {Fieus  elastiea).  In  the  former  the 
epidermis  is  in  two  layers,  and  in  the  latter  sometimes  as  much 
as  four.  This  point  can  only  be  determined  by  making  com- 
parative sections  of  very  young  leaves  and  okl  loaves.  Note 
the  depressed,  cistern-Hke  pits  in  the  oleander  leaf,  into 
which  the  stomata  open. 


54     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

(e)  Root  hairs  may  be  studied  in  cross-  or  longitudinal-sec- 
tions of  the  young  roots  of  seedlings  that  have  been  germinated 
between  damp  cloth  or  paper,  or  in  moist  air.  By  adding  a 
rather  strong  sugar,  or  potassium  nitrate  solution  the  cyto- 
plasm may  be  drawn  away  from  the  walls  sufficiently  (plas- 
molyzed)  to  become  visible. 

(/)  The  leaves  of  various  grasses  (e.g.  Panicum  capillare) 
will  show  simple  one-celled  hairs.  The  petunia  stem  possesses 
unbranched  hairs,  consisting  of  rows  of  cells.  Many  will  be 
found  to  terminate  in  glandular  cells.  Hairs  of  these  same  types 
ma}^  be  found  on  tobacco,  various  species  of  Silene  and  very 
many  other  plants. 

(g)  The  stems  and  leaves  of  various  crucifers  (e.g.  Erysi- 
mum, Arabis,  Bursa),  show  bifid  hairs.  Stellate  and  peltate 
hairs  are  shown  best  on  the  leaves  of  species  of  Elaeagnus  and 
Shepherdia. 

(h)  The  hairs  of  the  common  mullein  (Verbascuin  thapsvs) 
may  be  studied  as  examples  of  greatly  branched  hairs. 

(i)  Cross-sections  of  the  leaf  or  stem  of  nettle  (Urtica  and 
related  genera)  will  show  the  peculiar  stinging  hairs.  Under 
high  power  note  the  terminal  knob  which  breaks  off  as  the  hair 
penetrates  the  skin,  thus  permitting  the  distended  base  of  the 
turgid  hair  to  contract  and  discharge  the  poisonous  contents 
into  the  skin. 

77.  The  Conducting  System.  In  most  of  the  lower 
algae  and  in  the  fungi,  the  plant  body  consists  of  separate 
branching  filaments,  which  are  in  some  cases  woven 
together  into  a  more  or  less  firm  body.  These  filaments 
are  about  alike,  and  are  mostly  not  differentiated  into 
conducting  and  other  filaments.  In  some  of  the  more 
massive  algae,  however,  as  in  the  larger  kelps  (Laminaria, 
etc.),  or  rock  weeds  (Fucus,  etc.),  the  internal  cells 
are  much  more  elongated,  and  seem  to  conduct  the 
elaborated  food  stuffs  from  one  part  of  the  plant  to  the 
other,  true  sieve  tissue  sometimes  being  present.  A 
system  of  water-conducting  tissue  is  not  evolved  until 
the  Mosses  are  reached.  Here  the  center  of  the  stem  is 
occupied  by  elongated  cells,  that  serve  probably  in  part 


VASCULAR  BUNDLES  55 

as  water-conducting  cells,  in  part  probal^ly  for  support. 
Around  these  are  somewhat  elongated  thin-walled  cells 
that  are  possibh^  food-conducting  in  function. 

78.  It  is  in  the  higher  plants,  however,  the  Ferns  and 
Fern  Allies  and  Seed  Plants,  that  a  true  conducting 
system  is  developed.  This  consists  usually  of  strands  of 
tracheary  and  sieve  tissue,  each  associated  with  some 
living  parenchyma  cells,  passing  longitudinally  through 
the  stems  and  roots  and  out  into  the  leaves.  These 
strands  are  called  vascular  bundles. 

79.  A  vascular  bundle  consists  of  two  parts  which  are 
distinguished  both  structurall}^  and  functionally.  Xylem 
is  the  name  given  to  that  part  of  a  vascular  bundle 
consisting  of  the  tracheary  tissue  and  the  parenchyma 
associated  with  it.  Its  function  is  primaril}-  water- 
conducting.  The  phloem,  on  the  other  hand,  consists 
of  the  food-conducting  sieve  tissue,  with  the  accom- 
panying parenchyma  in  the  form  of  companion  cells, 
sieve  parenchyma,  etc.  Frequently  fibrous  tissue  is 
found  intimately  connected  with  the  xylem  and  phloem, 
usually  in  the  form  of  wood  fibers  with  the  former  and 
bast  fibers  with  the  latter.  In  such  a  case,  we  find  the 
supporting  S3'stem  to  be  partially  united  with  the 
conducting  system. 

80.  The  vascular  bundles  originate  in  the  growing 
points  by  the  conversion  of  certain  of  the  rows  of  meris- 
tem  cells  into  strands  of  elongated,  rather  narrow  cells. 
These,  bej'ond  elongating  considerably  and  dividing 
longitudinally  so  as  to  become  narrow,  retain  their 
meristematic  character  long  after  the  surrounding 
tissues  have  acquired  the  more  permanent  forms. 
They  are  then  kno\vn  as  procambium  or  as  procambial 
strands.  Eventually,  the  cells  composing  them  bc^gin  to 
change    into    the    permanent    tissues,     these    changes 


56     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

taking  place  first  in  a  few  cells  and  finally  including  all 
the  procambium  in  the  so-called  closed  bundles  or 
leaving  a  sheet  of  unchanged  meristem  between  the 
xylem  and  phloem  in  the  so-called  open  bundles. 

81.  Classifying  them  by  the  relative  positions  of  the 
xylem  and  phloem  parts  of  the  bundle,  we  may  dis- 
tinguish three  main  types  of  vascular  bundles,  radial, 
concentric,  and  collateral.  In  the  radial  type,  the 
xjdem  is  present  in  two  to  many  radially  situated,  more 
or  less  flattened  strands,  which  may  or  may  not  reach 
the  center.  Alternating  with  these  are  the  masses  of 
phloem.     In  the  concentric  type,  the  xylem  is  central 

and  is  surrounded  by  an  al- 
most continuous  layer  of 
phloem,  or  much  more  rarely 
phloem  and   xylem   have  re- 

FiG.  23.— Plans  of  radial,  concentric,    Verse     pOSitioUS.       In     the    Col- 
and  collateral  vascular  bundles.         ,     .  ,    ,  , ,  , 

lateral  type,  the  xylem  occu- 
pies one  side  of  the  bundle  (usually  that  toward  the 
center  of  the  stem),  and  the  phloem  the  other  side 
(usually  the  centrifugal  side). 

82.  The  radial  vascular  bundle  is  typical  of  roots. 
It  occupies  that  part  that  was  marked  off  as  plerome  at 
the  growing  point.  Bounding  it  is  a  layer  of  rather  thick- 
walled  cells,  often  with  suberized  or  cutinized  walls,  the 
endodermis  (or  bundle  sheath) .  This  is  actually  the  inner 
layer  of  the  cortex,  and  is  not  really  a  part  of  the  bundle 
itself.  Within  this  is  a  delicate  layer  of  thin-walled  cells, 
the  pericycle  (or  pericambium).  Bordering  on  this, 
or  in  some  families  of  plants  interrupting  it,  and  therefore 
touching  the  endodermis,  are  the  xylem  strands.  These 
are  made  up  of  tracheary  tissue.  The  elements  vary  in 
size,  the  smallest  (those  first  differentiated  from  the  pro- 
cambium)  being  those  next  to  the  pericycle,  those  lying 


RADIAL,  AND  CO^X'EXTRIC  BUNDLES  57 

nearer  the  center  being  gradually  larger.  The  various 
xylem  strands  may  meet  in  the  center  in  one  large  vessel 
or  in  a  mass  of  tracheary  elements,  or  the  center  may 
consist  of  parenchyma,  or  of  sclerenchyma,  or  even  of 
fibrous  tissue.  Midway  between  the  xylem  strands, 
and  like  them  bordering  upon  the  pericycle  are  smaller 
or  larger  phloem  masses,  consisting 
mainly  of  large  sieve  tubes,  and  small 
companion  cells,  and  other  parenchyma 
cells.  The  tissue  between  the  phloem  ^^^  24— Half  of 
and  xylem  strands  may  be  parenchyma  |  radial  vascular 
or  in  part  fibrous  or  sclerenchyma. 

83.  Lateral  roots  arise  by  the  conversion  of  portions 
of  the  pericycle  into  active  meristem  cells  which  soon 
become  arranged  in  definite  layers,  as  in  the  growing 
root  tip.  This  rootlet  forces  its  way  out  through  the 
cortex  until  it  reaches  the  outside.  The  plerome  part 
becomes  the  vascular  bundle  whose  tracheary  and  sieve 
elements  are  connected  respectively  with  the  xylem  and 
phloem  strands  of  the  main  bundle. 

84.  The  concentric  type  of  bundles  is  found  mainly 

in  the  stems  and  leaves  of  Ferns  and 
Fern  Allies.  In  these  plants  the  stem 
usually  possesses  several  vascular  bun- 
dles, which  may  be  variously  located 
Fio.  25.— Concentric     ^ud    of   different     shapes    and    cross- 

vascular  bundle.  '■ 

sections.  They  branch  more  or  less 
frequently  and  in  some  cases  anastomose  very  freely. 
Some  of  the  bundles  pass  out  from  the  stem  into  the 
leaves,  there  to  branch  again  to  form  the  veins.  In 
general,  the  bundle  consists  of  a  plate  of  xylem,  sur- 
rounded on  all  sides  or  on  all  except  the  edges  of  the 
plate,  by  large  sieve  tubes  and  small  parenchyma  cells. 
Around  these  are  often  one  or  more  layers  of  starch-bear- 


5S     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

ing  cells,  with  usually  a  thick-walled  bundle  sheath  about 
the  whole.  In  some  species  of  Lycopodium  there  are 
several  plates  of  xylem  alternating  with  phloem,  with 
one  bundle  sheath  around  all.  Transitional  forms  are 
found  between  this  type  and  the  radial  type  of  bundle  on 
the  one  hand  and  the  collateral  on  the  other. 

85.  The  collateral  type  of  bundle  is  present  in  stems 
and  leaves  of  Seed  Plants,  and  of  many  of  the  Fern  Allies. 
Three  types  may  be  distinguished,  open  collateral, 
closed  collateral,  and  bicoUateral.  The  first  two  differ 
in  the  presence  or  absence,  respectively,  of  a  layer  of 
meristem  cells  (cambium)  between  the  xylem  and  phloem, 
while  the  third  type  is  characterized  by  the  presence  of 
a  layer  of  phloem  on  the  inner,  as  well  as  on  the  peripheral 
side  of  the  xylem. 

86.  The  closed  collateral  type  of  bundles  is  especially 

characteristic  of  the  class  Monocotyle- 
doneae.  It  is  usually  associated,  also,  with 
a  scattered  arrangement  of  the  bundles  in 
the  stem.  There  is  usually  less  anas- 
tomosing of  such  bundles  with  each  other 
than  is  the  case  in  the  open  collateral  type. 
Fig.  26.—  This  type  is  present  in  some  of  the  Dicotyle- 
vlsculr^bundie!^  doneac  as  well,  but  not  so  frequently  as  the 
open  collateral  type.  As  an  example  that 
may  be  easily  obtained  to  study,  the  vascular  bundle 
of  Indian  corn  may  be  taken.  In  this  the  xylem  portion 
shows,  in  cross-section,  four  (rarely  three  or  five)  large 
vessels,  of  which  two  (annular  or  spiral)  are  placed  in 
the  radial  plane,  and  the  other  two  (large  pitted  vessels) 
lie  a  little  externally  to  and  to  the  right  and  left  of  these 
two.  Between  these  large  pitted  vessels,  and  bordering 
the  outermost  of  the  other  two  vessels,  is  a  mass  of  smaller 
cells,  sometimes  fibrous,  sometimes  tracheary  in  nature. 


COLLATERAL  BUNDLES  59 

The  innermost  vessel  borders  a  large  intercellular  air 
space.  Partly  enclosed  between  the  large  ]Mtted  vessels, 
but  in  the  main  placed  peripherally  to  the  X3dem,  is 
the  phloem.  In  cross-section  this  is  elliptical  and 
consists  of  large  sieve  tubes  and  small  companion  cells. 
The  whole  bundle  is  surrounded  by  a  mass  of  cells,  mainly 
fibrous.  No  meristem  tissue  is  present  at  all  in  the  com- 
j:)leted  bundle. 

87.  Open  collateral  vascular  bundles  can  be  found 
most  typically  in  the  class  Dicotyledoneae,  though  they  are 
also  present  in  the  Strobilophyta  and  related  groups. 
In  the  stem  they  are  usually  placed  almost  equidistant 
from  the  center,  surrounding  a  central  mass  of  paren- 
chyma, the  pith,  and  separated  from  each 

other   laterally   by   the    masses  of  paren- 
chyma  (primary    medullary   rays),    which 
connect  the  pith  to  the  cortex.     The  ten-      t^TYK^^ 
dency  to  anastomose  is  very  great  in  open 
collateral  bundles,  so  that  these  medullary     p^^  07—0  en 
rays  are  interrupted  above  and   below  at  cuilTrTundk  "^  ^ ' 
frequent  intervals,  and  are  not  continuous 
for  a  long  distance  in  the  stem.     Bicollateral  bundles  of 
the  open  collateral  type  are  similarly  placed  in  the  stem. 

88.  When  first  completed,  the  xylem  portion  consists 
of  two  or  three  to  several  rows  of  tracheary  tissue,  usually 
not  crowded  but  loosely  placed  with  reference  to  each 
other,  and  with  the  spaces  filled  in  with  parenchyma. 
The  outer  boundary  of  the  xylem  is  parallel  to  the 
surface  of  the  stem,  and  is  succeeded  by  a  layer,  one  to 
several  cells  thick,  of  meristem,  the  so-called  cambium. 
Bounding  this  externally  is  the  phloem  region,  consisting 
at  first  of  sieve  and  companion  cells  and  other  par- 
enchyma tissue,  and  sometimes  even  of  masses  of  bast 
fibers.     In  young  woody  stems  there  may  be  considerable 


60     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

fibrous  tissue  among  the  tracheary  tissue.  In  bicol- 
lateral  vascular  bundles,  the  inner  mass  of  phloem  is  not 
separated  from  the  xylem  by  a  cambium  layer. 

89.  Wherever  a  leaf  is  attached,  one  or  more  vascular 
bundles  in  the  stem  pass  out  into  it.  These  usually  run 
downward  in  the  stem  for  some  distance  before  they 
unite  with  the  other  bundles  there.  In  the  leaf  the 
phloem  portion  is  downward  (i.e.  toward  the  back  of  the 
leaf),  and  the  xylem  mass  uppermost.  Here  the  bun- 
dles are  the  so-called  'Veins."  At  first 
they  are  much  like  the  stem  bundles, 
although  usually  the  cambium  is  lack- 
ing, but  the  more  they  are  divided,  the 
smaller  and  simpler  they  become  until 
finally  they  may  consist  of  only  one  or 
two   rows  of  tracheids,  a  single  row  of 

of  a°vas^cuiTr^bu1idfe.  slcvc  cells,  and  a  row  of  companion  cells, 
with  a  few  thin-walled  parenchyma  cells 
surrounding  the  whole.  In  some  cases  these  bundles 
end  blindly  in  the  parenchyma  of  the  leaf.  In  other 
cases  they  meet  other  similar  bundles  and  so  form  a  net- 
work with  no  free  ends. 

90.  Secondary  Thickening.  The  fact  that  in  the  for- 
mation of  the  open  collateral  bundles  from  the  pro- 
cambial  strands  of  meristem  tissue,  a  portion  of  the 
meristem  remains  unchanged  as  the  cambium  layer, 
separating  the  xylem  and  phloem,  makes  it  possible  for 
the  bundle  to  continue  to  grow  in  thickness.  This  it 
does  by  the  growth  and  periclinal  division  of  the  cambium 
cells,  and  the  transformation  of  the  inner  cells  thus 
formed  into  xylem  and  of  the  outer  ones  into  phloem, 
continually  leaving,  however,  an  intermediate  portion  of 
cambium  which  can  grow  and  divide  further. 

91.  The  xylem  formed  during  the  process  of  secondary 


SECONDARY  THICKENING  61 

thickening  diflers  usually  quite  materially  from  the  pri- 
mary xylcm.  It  contains  much  more  fibrous  tissue,  is 
more  compact,  and  forms  a  true  wood.  The  phloem 
also  is  interspersed  with  more  bundles  of  bast,  and  may 
by  its  formation  soon  crush  out  of  recognizable  shape  the 
primary  phloem.  In  addition,  the  tissues  forming  the 
primary  medullary  rays  become  active.  The  layer  of 
parenchyma  cells  that  connects  the  edge  of  the  cambium 
of  one  bundle  with  that  of  the  next  bundle  becomes 
itself  converted  into  cambium  by  the  accumulation  of 
large  amounts  of  cytoplasm  in  the  cells,  and  the  formation 
of  periclinal  walls.  Part  of  this  interfascicular  cambium 
thus  formed  gives  rise  only  to  cortical  and  medullary 
parenchyma,  but  at  intervals  new  bundles  arise  by  the 
formation  of  xylem  and  phloem,  respectively,  on  the 
inner  and  outer  faces  of  the  cambium  layer.  Thus,  sec- 
ondary bundles  are  formed,  which  divide  the  medullary 
rays  longitudinally,  and  as  the  bundles  become  more  and 
more  numerous,  these  primary  rays  may 
eventually  be  reduced  to  thin  plates  of  paren- 
chyma, only  one  or  two  cells  thick,  and  per- 
haps only  a  few  cells  wide  (measured  in  ver- 
tical direction),  but  still  extending  from  the 
pith  to  the  cortex.  Additional  (''second- 
ary") medullary  rays  are  formed  within  the  Fiq.  29.— 
bundles  when  certain  cambium  cells  cease  grmvth  of l*^'"- 
to  form  xylem  elements  and  from  that  time 
forward  produce  parenchyma  cells.  These  secondary 
medullary  rays  usually  arise  at  varying  distances  from 
the  center,  a  certain  number  of  new  ones  being  laid  down 
each  3'ear. 

92.  Where  the  growth  is  continuous  and  (Hjual.  the 
wood  is  usually  of  fine  grain  and  uniform.  Most  woody 
plants  of  the  temperate  zones,   however,   and  of  those 


62     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

portions  of  the  tropics  where  there  are  marked  wet  and 
dry  seasons  have  annual  growth  periods,  separated 
by  seasons,  where  growth  ceases  entirely  or  nearly  so. 
In  such  cases  the  first  part  of  the  xylem  laid  down  each 
year  consists  of  a  greater  proportion  of  tracheary  elements 
and  fewer  wood  fibers,  the  proportion  of  the  latter  in- 
creasing as  the  season  progresses.  The  wall  of  each 
successive  fiber  is  thicker  and  the  lumen  smaller. 
Such  tracheae  as  are  produced  later 
in  the  season  are  smaller  than  those 
first  formed.  The  contrast  of  these 
small  thick- walled  numerous  wood 
fibers,  produced  at  the  close  of  one 
season's  growth,  and  the  large  lu- 
mened  tracheary  and  wood  cells 
Fig.  ao.^th^wth  rings  formcd  at  the  beginning  of  the  next, 
in  .tern  of  oak  ^^^^^    ^    ^^^^    distinct     line    and 

marks  off  the  growth  rings,  which,  as  they  are  usually 
annual,  are  of  great  value  in  determining  the  age  of  a 
tree. 

93.  Usually  the  wood  nearest  the  center  of  a  tree 
undergoes  changes  after  it  has  reached  a  certain  age. 
Among  these  changes  are  the  deposition  in  the  lumina 
of  the  cells  of  various  organic  substances,  which  seem 
to  make  the  tracheary  elements  no  longer  able  to  carry 
water,  and  the  death  of  all  living  cells  (e.g.  cells  of  medul- 
lary rays,  wood  parenchyma,  etc.),  and  often  a  change  in 
color.  Such  wood  is  called  heart  wood,  to  distinguish 
it  from  the  water-conducting  sap  wood,  in  which  the 
medullary  rays  and  wood  parenchyma  cells  are  still  alive. 

Laboratory  Studies,  (a)  By  studying  successive  thin  cross- 
sections  of  the  stem,  bej^innin^  at  the  growing  point,  there  will 
be  found  the  procambial  strands,  which  give  rise  to  the  vascular 
bundles.     They  appear,  in  cross-section,  as  masses  of  cells  of 


LABORATORY  STUDIES  63 

small  diameter.     Further  down,  part  of  these  strands  will  be 
found  to  consist  of  tracheary  tissue. 

(b)  Study  a  vascular  bundle  of  the  radial  type,  by  making 
cross-sections  of  the  larger  roots  of  corn,  iris,  hyacinth,  or  of 
the  main  roots  of  seedlings  of  bean,  pea,  sunflower,  etc.  Note 
the  number  of  xylem  i)lates,  location  and  extent  of  phloem,  the 
endodermis,  pericycle,  etc. 

(c)  Make  longitudinal  sections  of  the  same  kinds  of  roots, 
and  identify  the  tissues  shown  in  cross-section. 

(d)  Using  a  bean  seedling,  in  which  lateral  rootlets  have 
begun  to  show,  make  numerous  cross-sections,  so  as  to  find  such 
rootlets  in  various  stages  of  development,  and  study  their  or- 
igin and  mode  of  emergence. 

(e)  The  concentric  type  of  bundle  may  be  studied  best  in 
cross-sections  of  the  rhizomes  of  the  brake  {Pteridium  aqni- 
linum).  Make  a  longitudinal  section  also,  so  as  to  identify  the 
tissues  present. 

(/)  Vascular  bundles  that  may  perhaps  be  assigned  to  the 
concentric  type  may  be  studied  in  cross  and  longitudinal 
sections    of  the  stems  of  Selaginella  and  Lycopodium. 

{g)  Make  cross  and  longitudinal  sections  of  the  stem  of 
Indian  corn,  sugar  cane,  Smilax  hcrbacea,  or  other  mono- 
cotyledons, for  vascular  bundles  of  the  closed  collateral  type. 
Note  their  distribution  in  the  stem. 

(h)  Open  collateral  bundles  may  be  studied  to  advantage  in 
the  younger  internodes  of  clover  and  alfalfa,  or  the  upper  ones 
of  sunflower.  Note  the  arrangement  of  the  various  xylem 
elements.     Note  how  the  l)undles  are  distributed  in  the  stem. 

(i)  Study  the  lower  internodes  of  the  same  j^lants,  for  secon- 
dary thickening.  Note  the  differences  between  the  secondary 
xylem  and  that  formed  in  the  bundle  before  the  secondary 
thickening  had  begun.  Note  the  secondary  vascular  bundles, 
interfascicular  cambium,  etc. 

(j)  Make  and  study  a  cross-section  of  a  two-year-old  twig  of 
basswood,  elm,  or  other  tree.  Note  the  growth  rings,  and  in 
cross  and  longitudinal  sections  determine  their  structure. 
Study  the  })rimar3'  and  secondary  medullary  rays. 

{k)  For  bicollateral  vascular  bundles,  the  best  objects  are 
the  stems  of  Cucurbitaceae,  e.g.  squash,  cucumber,  etc., 
although  they  are  found  also  in  the  Solanaceae,  e.g.  young(>r 
parts  of  the  stems  of  petunia,  potato,  etc. 


64     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

(/)  Reduced  bundles  and  bundle  endings  can  be  studied  in 
leaves  and  petals  by  placing  them  in  some  clearing  fluid,  e.g.  a 
mixture  of  phenol  (carbohc  acid),  and  turpentine  after  15  to  20 
minutes'  treatment  with  95  per  cent  alcohol.  Mount  in  the 
same  fluid  and  examine  under  low  and  high  powers.  If  these 
objects  are  previously  placed  with  their  cut  ends  in  an  aque- 
ous safranin  or  eosin  solution  until  the  colored  Hquid  has 
filled  the  bundles  these  are  more  conspicuous. 

(w)  Examine  the  cut  ends  of  logs  and  stumps  of  various  kinds, 
to  distinguish  the  heart  wood  and  sap  wood.  That  they  are 
different  in  some  of  their  chemical  characteristics  will  be  shown 
by  their  different  proneness  to  decay. 


94.  The  Supporting  System.  In  many  plants  the 
supporting  and  conducting  systems  are  intimately 
connected,  the  vascular  bundles  containing  not  only  the 
conducting  cells  but  also  an  abundance  of  wood  and  bast 
fibers.  However,  at  first  the  stems  are  often  supported 
by  other  means.  Thus,  a  strong  development  of 
coUenchyma  strands  under  the  epidermis  is  a  very  com- 
mon occurrence.  By  the  natural  turgor  and  growth 
of  the  stem,  these  collenchyma  strands  are  stretched, 
and  thus  stiffen  the  stem  until  the  fibrous  tissues 
are  developed  later  in  connection  with  the  vas- 
cular bundles.  In  the  cortex,  bast  bundles  are  fre- 
quently encountered,  inde- 
pendent of  any  vascular 
bundles.  In  the  stems  of 
Ferns  and  Fern  Allies,  large 
bundles  of  fibrous  tissues  are 

in 

(3)  scattered  here  and  there. 
Closely  allied  to  the  support- 
ing system  of  tissues,  in  function,  are  those  tissues  that 
serve  for  protection,  as  for  example,  the  sclerenchyma, 
deposited  in  various  parts  of  the  plant,  such  as  the 
bark,  roots,  fruits,  and  seeds. 


Fig.  31. — Supporting  system 
stems  of  'fl)  moss,  (2)  fern, 
flowering  plant. 


NUTRITIVE  TISSUES 


Go 


95.  Ill  addition  to  the  conducting  and  supporting 
systems,  the  remainder  of  the  plant  serves  various 
functions.  Thus,  a  large  portion  of  green  plants  con- 
sists of  nutritive  tissues.  These  are  usually  found  in 
leaves,  but  are  also  present  in  the  younger  parts  of  stems. 
In  leaves  we  can  usually  distinguish,  underneath  the 
upper  epidermis,  one  or  more  rows  of  closely  packed 
cells,  with  their  long  axes  perpendicular  to  the  surface 
of  the  leaf,  forming  the  so-called  pali- 
sade parenchyma.  In  leaves  equally 
lighted  on  both  sides,  this  palisade 
parenchyma  is  often  formed  on  both 
surfaces.  Below  the  palisade  layers 
the  assimilative  cells  are  looser,  form- 
ing the  "sponge"  parenchyma,  with 
larger  intercellular  spaces  between  them, 
which  connect  with  the  exterior  through  the  stomata. 

96.  The  system  of  intercellular  spaces  is  quite  marked 
in  all  higher  plants.     These  passages  are  usually  con- 


32.— Section  of 
a  leaf. 


Fig.  33. — Large  intercellular  spaces  in 


■r-lily  petiole,  and  rush  stem. 


tinuous  through  the  petioles  of  the  leaves  into  the  stems 
and  down  into  the  roots.  In  plants  growing  in  swampy 
places  or  in  water  these  intercellular  spaces  are  very 
much  enlarged  and  apparently  serve  the  double  function 
of  providing  an  ample  air  supply  to  the  submerged  por- 


6G     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 


Fig.  34.— Starch 
storage  cells  of 
potato. 


tions  of  the  plant  and  of  giving  buoyancy  to  the  part  in 
which  they  occur. 

97.  Another  important  function  of  tissues  is  that  of 
storage  of  food  substances.  Storage  tissues  are  usually 
composed  of  large  parenchyma  cells 
with  large  central  vacuoles  and  compara- 
tively' little  protoplasm.  In  some  special 
cases  where  the  storage  product  is  one 
of  the  hemicelluloses  this  is  deposited 
against  the  cell  wall  forming  a  sort  of 
sclerenchyma  tissue. 

98.  In  many  plants  are  found  secretory 
cells.  These  often  line  closed  cavities 
(or  ''reservoirs")  or  elongated  passages.  These  cavities 
or  passages  may  be  formed  simply  by  the  pushing 
apart  of  certain  cells  as  the  secretion  is  poured  into 
the  space  between  them  (i.e.  produced  schizogenously) 
or  certain  cells  may  be  dissolved,  forming  ''lysigenous" 
cavities.  Good  examples  of 
the  first  type  are  shown  by 
the  gum  canals  of  the  ivy 
{Hedera  helix)  and  the  tur- 
pentine canals  of  conifers  or 
the  glands  of  the  leaves  of  St. 
John's     wort      (Hypericum). 

In  the  leaves  and  fruits  of  Rutaceae  the  cavities  more 
often  arise  by  the  dissolving  of  the  secretory  cells  thus 
setting  free  the  secretion  within  a  cavity.  The  secretions 
are  usually  gums  or  ethereal  oils,  often  containing  resins, 
etc.  Other  cells  containing  crj^stals  of  calcium  oxalate 
and  other  substances,  perhaps  including  tannin,  may 
possibly  be  classed  as  excretory  organs  in  which  the 
excretions  are  stored  up  in  the  absence  of  any  structure 
that  would  permit  their  being  thrown  out  of  the  plant. 


Fig.  35. — Gum  and  turpentine 
canals  of  ivy  and  pine. 


CORK  67 

Externally  there  ma}-  be  developed  secretor}^  structures 
such  as  the  nectaries  of  flowers,  etc. 

99.  Cork.     At  first  the  cutinized  external  wall  of  the 
epidermis  of  the  stem  serves  to  prevent  excessive  water 
loss.     When  the  stem  enlarges  the  increased  circumfer- 
ence is  met  by  the  enlargement  or  multiplication  of  the 
epidermal  cells.     There  is  a  limit,   however,   for  most 
stems  to  this  epidermal  growth  and  furthermore  as  the 
stem  becomes  enlarged  the  one  layer  of  cells  is  no  longer 
sufficient  protection  against  water  loss  and  especially 
against  mechanical  injury.     There  is  accordingly  formed 
beneath  the  epidermis  a  layer  of  meristem  cells  called 
phellogen  or  cork  cambium,  which  gives  rise  (by  periclinal 
divisions)   to  radial  rows  of  cells  without  intercellular 
spaces,  whose  walls  become  strongly  suberized  by  the  de- 
position   within    them    of    a    _______ 

fatty  substance  or  substances    P^r^^^  ^^-^^^~^>""---v^ 
called   suberin,  which   makes     ^Eizt  ^'^^--^  Ij^A 
them  impermeable  to  water.      ^B=^H      /"    ^\  ^A 
The  cells  die  shortly  after  sub-     ^^^^^ 
erization  occurs  and  remain    Fig.  36— Cork  (i),  subepidermal, 
filled  with  the  broken-down 

protoplasm  or  become  filled  with  air.  These  layers  of 
cork  cells,  owing  to  the  suberization,  cut  off  the  passage 
of  water  toward  the  exterior  and  the  epidermal  cells 
accordingly  die.  With  the  growth  of  the  stem  in 
circumference  these  are  soon  ruptured  here  and  there 
and  gradually  peel  off.  Since  the  outer  cork  cells  are 
also  dead  they  cannot  enlarge  and  so  as  the  stem 
grows  longitudinal  fissures  occur  in  the  cork  extending 
down  nearly  to  the  living  phellogen,  which  however 
being  alive  is  able  to  increase  in  circumference  and 
thus  keep  pace  with  the  increasing  circumference 
of   the   stem.     Sometimes    this  phellogen  layer  is  per- 


68     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS  ' 

manent  but  more  often  a  layer  of  cells  starting  at  the 
phellogen  and  dipping  inward  into  the  cortex  and  finally 
back  to  the  phellogen  also  becomes  converted  into 
phellogen  and  begins  to  produce  cork.  The  more  or 
less  lens-shaped  mass  of  tissue  cut  off  by  this  process 
promptly  dies  from  lack  of  water  and  eventually  scales 
off.  Thus  is  formed  the  flaky  type  of  bark.  This  proc- 
ess is  repeated  time  and  again  so  that  the  bark  remains 
only  about  the  same  thickness,  no  matter  what  the  age 
of  the  tree. 

100.  Lenticels.  As  cork  is  about  to  form,  a  phellogen 
of  special  type  arises  under  many  of  the  stomata  on  the 

young  stems  and  twigs.  This  forms 
a  loose  mass  of  cork  with  large  inter- 
cellular spaces  connecting  through 
the  intercellular  spaces  in  the  phel- 
logen (these  being  lacking  in  ordinary 
Fig.  37.— Lenticels.  phcllogeu  and  cork)  with  those  of  the 
cortex.  This  mass  of  cork  cells  rup- 
tures the  epidermis  and  forms  a  minute  lens-shaped 
fleck.  These  lenticels  function  then  as  openings  for  the 
exchange  of  gases  while  at  the  same  time  the  mass  of 
loose  cork  cells  greatly  reduces  the  water  loss. 

101.  In  addition  to  the  foregoing  cases  cork  is  also 
formed  in  many  plants  as  a  result  of  wounds.  The 
injured  cells  die  but  those  immediately  or  but  a  short 
distance  below  become  converted  into  phellogen  which 
produces  a  cork  layer  that  forms  an  effective  barrier 
against  further  water  loss  and  probabl}^  also  prevents  in  a 
large  measure  the  entry  of  foreign  organisms.  Fre- 
quently this  cork  thus  formed  serves  as  an  abscission 
layer,  i.e.  it  splits,  and  permits  the  dead  tissues  to  slough 
off.  The  layers  normally  found  at  the  base  of  the  leaf 
petiole  in  the  autumn  are  of  similar  nature,  serving  to 


LABORATORY  STUDIES  69 

permit  the  fall  of  the  leaves  and  at  the  same  time 
covering  the  exposed  surface  with  a  cork  laj-er  which 
prevents  the  loss  of  water  or  entry  of  harmful  organisms. 

Laboratory  Studies,  (a)  Examine  the  cross-section  of  a 
very  young  twig  of  elder  or  of  a  young  stem  of  lamb's  quarters 
{Chenopodium  album)  and  note  the  supporting  system  which 
at  this  stage  consists  of  longitudinal  strands  of  stretched 
elastic  collenchyma  just  under  the  epidermis. 

(b)  In  older  parts  of  the  stem  of  the  same  plant  note  how  the 
main  supporting  function  has  been  assumed  b}^  the  wood  fibers 
associated  with  the  xylem  of  the  vascular  bundles  and  by 
strands  of  bast  fibers  sometimes  closely  associated  with  the 
phloem  of  the  same  bundles  and  sometimes  independent  of  any 
bundles. 

(c)  Make  a  cross-section  of  a  leaf  of  beech  or  lily  or  other 
plant  and  examine.  The  special  nutritive  palisade  tissue  is 
present  next  to  the  upper  epidermis.  In  the  lower  part  of  the 
leaf  note  the  ''sponge"  parenclwma  with  its  large  intercellular 
spaces.  The  leaf  of  cottonwood  (Populus  sp.),  compass  plant 
{SUphium  laciniatum) ,  etc.,  will  show  palisade  tissues  on  both 
sides. 

((/)  ]\Iake  a  cross-section  of  a  stem  of  a  water  lily  (Castaha, 
Nelumbo,  etc.)  or  of  a  rush  (Juncus)  or  of  some  other  semi- 
aquatic  or  aquatic  plant.  Note  the  large  intercellular  spaces. 
Note  also  the  rather  small  development  of  water-conducting 
tissues. 

(e)  For  examples  of  tissues  devoted  to  storage  purj^oses 
study  sections  of  a  tuber  of  potato,  root  of  sweet  potato,  i)ith 
of  twig  of  apple  or  sassafras,  seed  of  date,  etc. 

(/)  Make  a  cross-section  of  the  stem  of  iv}^  {Hedera  hcU.r) 
for  gum  canals  lined  with  secretory  cells.     Similar  canals  in  the 
wood   and   leaves   of   Conifers    (pines,  spruces,  etc.)    contain 
turpentine. 

(g)  Make  a  cross-section  of  the  leaf  of  St.  John's  wort 
(Hypericum)  or  leaves  or  fruit  of  the  orange  or  lemon  (Citrus) 
for  secretory  reservoirs  ("glands")  in  the  tissue. 

(h)  Examine  various  flowers  and  study  the  location  and 
structure  of  the  nectaries.  Extra-floral  nectaries  may  1)C  found 
on  leaves  of  various  plants,  e.g.  some  of  the  plums.     Other 


70     GROUPS  OF  TISSUES,  OR  TISSUE  SYSTEMS 

types  of  glands  maj-  be  found  on  the  "tentacles"  of  the 
leaves  of  the  sun-dew  (Drosera). 

(i)  Section  a  very  young  twig  of  basswood  (Tilia)  or  elm  or 
other  tree  and  note  the  epidermis.  Compare  this  with  a  one 
or  two  year  old  twig  of  the  same  tree  and  note  the  cork  forma- 
tion. Studv  cross-sections  of  various  kinds  of  tree  trunks  and 
note  the  different  types  of  cork  formation  in  these. 

ij)  On  a  young  twig  of  elder  (Sambucus),  snowball  (Vibur- 
num) or  birch  (Betula)  section  the  lenticcls  in  different  stages 
of  development  and  study  them. 

(k)  In  the  autumn  make  longitudinal  sections  through  the 
base  of  the  petiole  of  leaves  of  maple,  elm  or  other  deciduous- 
leaved  trees.  If  made  at  the  proper  place  and  time  the  cork- 
like abscission  layer  may  be  found. 


REFERENCE  BOOKS 
The  books  enumerated  for  Chapters  I  and  II. 


CHAPTER  IV 
PLANT  PHYSIOLOGY 

102.  Plant  Physiology  has  for  its  subject  the  study 
of  the  activities  of  the  plant  and  of  its  parts.  It  is  not 
sufficient  to  learn  about  the  morphology,  i.e.  the  external 
and  internal  structure;  we  must  also  seek  to  learn  what 
the  different  parts  are  for,  how  the  plant  carries  on  its 
activities  and  the  relations  of  the  plant  to  the  external 
surroundings.  In  the  preceding  chapters  the  functions 
of  the  parts  have  been  mentioned  briefly  in  connection 
with  the  special  structures.  In  this  chapter,  it  is  sought 
to  take  up  the  plant  activities  as  a  whole.  Much  of 
what  is  here  given  can  be  used  by  the  skillful  teacher  at 
the  same  time  that  the  foregoing  chapters  are  being 
studied. 

Plant  Physiology  will  be  treated  under  the  following 
heads:  (1)  Nutrition,  (2)  Growth  and  Reproduction, 
(3)  Movements.  To  these  will  be  added  (4)  a  short 
consideration  of  the  Pathology  of  Plants. 

103.  Nutrition,  in  its  widest  sense,  includes  the  taking 
in  and  giving  out  of  water  and  other  substances,  their 
transportation  from  one  part  to  another  in  the  plant, 
their  use  in  the  plant  in  the  formation  of  food,  the  use 
of  this  food,  and  the  energies  required  or  set  free  in  all 
these  processes. 

104.  The  most  important  single  substance  taken  in 
by  a  plant  is,  beyond  doubt,  water.  The  driest  plant 
parts,  such  as  seeds,  possess  from  5  to  10  per  cent,  or 
more  of  water  while  leaves  may  possess  75  per  cent,  or 

71 


72  PLANT  PHYSIOLOGY 

even  greater  amounts.  Flesh}'  fruits  like  the  pear  and 
grape  contain  still  larger  amounts.  Algae  are  extremely 
watery,  the  amount  of  water  in  Spirogyra  probably  ex- 
ceeding 97  per  cent.  This  water  is  present  not  only 
in  the  vacuoles  but  also  in  the  cell  wall  and  protoplasm, 
both  of  which  have  the  property  of  imbibing  water  to  a 
considerable  extent.  Thus  even  lignified  cell  walls  may 
have  one-third  of  their  weight  as  water  and  protoplasm 
is  probably  not  active  unless  75  per  cent,  or  more  water 
is  contained  in  it. 

105.  This  water  is  almost  continuous  throughout  the 
whole  plant,  so  that  we  may  think  of  a  plant  as  a  mass 
of  water  of  the  shape  of  a  plant  with  the  interstices  oc- 
cupied here  by  molecules  of  cell  wall  substance,  there  by 
protoplasm,  the  water  being  continuous  also  with  the 
water  surrounding  the  roots  in  ordinary  plants,  or  the 
whole  plant  if  it  is  aquatic. 

106.  Although  the  water  is  continuous  throughout 
the  plant,  it  is  held  more  abundantly  in  some  parts  than 

others,  and  may  be  in  motion  within 
the  plant.  The  entry  of  water  into  a  cell 
is  through  the  process  called  osmosis. 
The  plasma  membrane  of  the  cell  is  a 
semipermeable  membrane  which  is  almost 
Fid.  38.— A  tur-  perfectly  permeable  to  water  but  almost 
moiyz^ed^ceu.  ^'^^"  impcrvious  to  somc  of  the  substances  in 
solution  in  the  water  of  the  cell.  Under 
such  circumstances,  if  the  solutes  inside  the  cell  are  more 
concentrated  than  those  outside,  the  molecules  of  water 
pass  more  rapidly  into  than  out  from  the  cell  and  it 
becomes  filled  with  water.  The  protoplasm  is  pressed 
against  the  cell  wall  and  this  stretches  until  it  may  be 
increased  in  area  in  some  cases  by  as  much  as  50  per  cent. 
This  stretching  continues  until  the  wall  can  stretch  no 


PASSAGE  OF  WATER  73 

more  or  until  the  counter  pressure  of  the  stretched  walls 
equals  the  osmotic  pressure  (i.e.  the  power  with  which, 
under  the  given  difference  in  density  of  the  outer  and 
inner  solutions,  the  water  from  the  outside  tends  to 
enter  the  cell).  Such  a  water-distended  cell  is  said  to  be 
turgid  or  in  a  state  of  turgor.  The  pressure  within  it 
may  equal  several  atmospheres.  Jost  gives  this  pressure 
for  some  desert  plants  as  equalling  one  hundred  atmos- 
pheres, i.e.  about  1500  pounds  per  square  inch. 

107.  If  a  cell  be  in  contact  with  a  plentiful  water 
supply,  it  will  become  as  turgid  as  the  difference  in 
osmotic  pressure  outside  and  inside  will  permit.  If  a 
cell  adjacent  to  it  is  not  in  contact  wdth  the  external 
water,  there  will  be  a  passage  of  water  from  one  cell  to  the 
other,  the  direction  depending  upon  which  cell  has  the 
denser  solution  in  its  cell  sap.  Thus,  in  a  plant  with  one 
part  exposed  to  evaporation  into  the  air  and  with 
the  other  part  in  water  there  will  be  a  constant  passage 
of  water  into  the  plant  and  up  through  it  from  cell  to 
cell,  by  osmosis,  and  out  into  the  air  by  evaporation  from 
the  wet  surface  of  the  cell  walls. 

108.  In  larger  land  plants,  however,  this  rather  slow 
passage  of  water  from  one  cell  to  another  b}^  osmosis  is 
too  slow  to  supply  the  aerial  parts  with  the  requisite 
amount  of  water.  Such  plants  possess  special  elongated 
cells  no  longer  living  and  often  with  the  separating 
partitions  dissolved  out,  viz. :  the  tracheae  and  tracheids. 
(See  paragraphs  46  to  49.)  These  serve  as  tubes 
through  whi(^h  the  water  rises,  not  as  a  simple  diffusion 
of  molecules  but  with  a  mass  motion,  i.e.  as  a  definite 
current  carrying  with  it  whatever  miiy  be  dissolved. 

109.  In  these  plants  then  we  can  trace  the  water 
through  the  following  steps  of  progress.  It  enters  the 
root  hairs  by  osmosis  from  the  surrounding  soil  where  it 


74  PLANT  PHYSIOLOGY 

is  present  in  thin  or  thick  films  around  the  soil  particles, 
the  entry  being  molecule  by  molecule.  It  passes  by 
osmosis  from  cell  to  cell  through  the  cortex  of  the  root 
until  the  tracheary  tissue  of  the  vascular  bundle  is 
reached.  It  enters  these  vessels  (just  by  what  force  is 
not  clear)  and  ascends  through  them  (also  by  what  force 
is  uncertain).  Some  of  it  is  taken  out 
by  osmosis,  by  various  parenchyma 
cells  (e.g.  medullary  rays)  bordering  the 
tracheary  tissue  and  passed  osmot- 
ically  to  the  various  tissues  at  that  ap- 
proximate level,  but  the  bulk  passes 
on  out  into  the  leaves  w^here  it  is  taken 

Fig.  39. — Course    of    ,  •       •     ^        n  i  n 

w  a  t  e  r    into,    and  by  osmosis  mto  the  parenchyma  cells. 

through    a  land  plant.    -^^  ,,  n      i  i       •  ii       i 

From  the  cells  bordermg  the  larger  air 
spaces,  it  evaporates  into  these  and  passes  as  vapor  out 
through  the  stomata. 

110.  The  evaporation  of  water  from  a  wet  membrane 
(e.g.  cell  wall)  makes  available  a  large  amount  of  energy 
for  lifting  up  water  to  replace  that  evaporated.  It  has 
been  shown  that  the  energy  thus  available  in  a  leaf  is 
many  times  more  than  that  necessary  to  lift  the  water 
up  to  the  tops  of  the  highest  trees  (150  meters).  How- 
ever, though  the  energy  is  ample,  the  air  pressure  at  sea 
level  is  only  sufficient  to  lift  water  not  quite  ten  meters 
into  a  vacuum.  The  osmotic  pressure  developed  in 
roots  that  are  rapidly  absorbing  water  is  enough  oc- 
casionally to  lift  water  to  a  height  of  eleven  meters  in  the 
grape  and  even  twenty-five  meters  in  the  Birch  (Betula 
In  tea).  The  distance  that  this  root  pressure  will  lift 
water  plus  the  height  air  pressure  will  lift  water  into  a 
vacuum  fall  far  short  of  the  distance  water  must  be 
lifted  in  tall  trees.  It  has  been  suggested  that  perhaps 
the   cohesion   that   exists   in   water   in   narrow   vessels 


PATH  OF  WATER  75 

(e.g.  in  tho  trachoaiy  tissues)  is  sufficient  to  pull  the 
water  u])  from  tlio  lowest  roots.  Other  investigators 
have  suggested  that  some  of  the  living  parenchyma  cells 
which  accompany  all  water-conducting  tracheids  and 
tracheae  are  concerned  in  the  lifting  of  the  water  (or 
ascent  of  sap  as  it  is  often  called). 

111.  Path  of  the  Water.  This  is  chiefly  in  the  cavities 
(lumina)  of  the  tracheary  tissue.  It  is  also  not  to  be 
denied  that  the  w^ater  will  pass  upw^ard  slowly  from  the 
roots,  passing  from  cell  to  cell  in  the  parenchyma  by 
osmosis,  for  the  tissues  above  ground  have  more  con- 
centrated solutions,  and  so  bring  about  osmosis  from  the 
root  cells  with  their  less  concentrated  solutions.  This  is, 
however,  not  sufficient  to  supply  an  ordinary  plant. 
Within  the  tracheary  tissue,  the  lumen  contains  not  only 
water  but  some  bubbles  of  air,  past  which  the  water  flows 
in  a  thin  film  next  to  the  cell  wall.  In  trees  the  central 
wood  after  a  number  of  years  suffers  deposition  of  resins 
or  other  insoluble  substances  within  the  cell  cavities  and 
possibly  walls  as  well,  so  that  w^ater  conduction  is  no 
longer  possible.  Such  wood  is  often  different  in  color 
and  is  called  heart  wood  and  contains  no  living  cells. 
The  unchanged  wood  around  it,  the  sap  wood,  contains 
dead  water-conducting  tracheary  tissue,  dead  fibrous 
tissue  and  living  wood  parenchyma. 

112.  The  evaporation  of  water  from  the  leaves  and 
stems  is  often  given  the  name  transpiration.  It  is  an 
unavoidable  loss  since  the  plant  must  have  openings, 
the  stomata,  through  the  epidermis,  for  the  purpose  of  gas 
exchange  and  when  these  are  open  the  loss  of  water  can- 
not be  jH-evented.  The  thickening  of  the  cuticle  in 
plants  of  dry  regions,  the  depression  of  stomata  in  the 
pits  to  provide  dead  air  spaces  outside,  the  formation  of 
thick  layers  of  hairs,  etc.,  all  indicate  that  it  is  not  to  the 


76  PLANT  PHYSIOLOGY 

advantage  of  a  plant,  to  have  transjnralion  taking  place 
but  just  the  contrary. 

113.  The  amount  of  water  given  off  by  transpira- 
tion is  very  large.  The  water  loss  from  a  Birch  tree, 
standing  alone  and  estimated  to  have  200,000  leaves  was 
calculated  by  von  Hohnel  at  about  500  liters  on  a  very 
hot  dry  day  and  about  60  to  70  liters  on  average  days. 
An  acre  of  hops  will  evaporate  three  million  to  four 
million  liters  of  water  in  a  season.  Dietrich  estimates 
that  for  every  gram  of  dry  substance  found  in  a  plant, 
from  250  to  400  grams  of  water  have  been  evaporated. 
In  twelve  hours,  a  grape  leaf  evaporates  as  much  water  as 
would  form  a  film  0.13  mm.  deep  over  the  whole  leaf, 
while  for  cabbage  and  apple  leaves  in  the  same  length  of 
time  the  figures  are  respectively  0.31  and  0.25  mm. 
In  one  season,  an  oak  tree,  during  the  time  it  holds  its 
foliage,  evaporates  an  amount  equivalent  to  33  mm.  over 
all  its  leaves.  An  open  water  surface  would  evaporate, 
in  the  same  time,  500  to  600  mm.,  showing  that  the 
evaporation  (transpiration)  is  far  less  from  the  leaves 
than  from  a  free  surface. 

114.  It  has  been  show^n  that  an  impermeable  surface 
with  very  numerous  openings,  as  for  example,  the 
epidermis  with  its  numerous  stomata,  evaporates  nearly 
as  much  water  as  if  it  were  a  free  water  surface.  The 
stomata,  however,  are  capable  of  closing  and  thus  almost 
wholly  preventing  water  loss  for  such  periods  of  time  as 
they  may  remain  closed.  At  night  they  are  nearly 
closed.  When  the  plant  begins  to  wilt,  it  has  been 
shown  that  they  also  close  automatically  through  re- 
duced turgor  of  the  guard  cells  thus  preventing  too  great 
a  loss  of  water.  All  physical  phenomena  which  increase 
evaporation  also  increase  the  water  loss  from  the  leaves 
as   long   as   the   stomata   remain   open,    e.g.    increased 


GUTTATIOX  77 

temperature  and  dryness  of  the  surrounding  air,   sun- 
shine, etc. 

115.  Many  plants  exude  water  from  specially  modified 
stomata  (the  so-called  water  pores)  at  the  edges  of  the 
leaves  when  the  movement  of  water  upward  has  been 
strong  and  then,  by  increase  of  the  humidity  of  the  air, 
the  evaporation  has  been  checked  rather  suddenly. 
This  may  take  place  in  the  form  of  drops  or  even  as  a 
fine  stream.  It  is  called  guttation.  Its  mechanics  and 
use  are  not  clear. 

Laboratory  Exercises.  Note  :  In  a  large  class,  many  of  these 
experiments  cannot  be  performed  by  every  student.  In  that 
case  the  instructor  should  assign  some  experiments  to  one 
student,  others  to  another  throughout  the  class  or  should  set 
up  the  experiments  himself  before  the  class.  In  either  case, 
every  student  should  make  complete  notes  upon  the  experiment 
for  himself. 

(a)  Weigh  a  handful  of  freshly  picked  leaves  quickly  before 
they  have  begun  to  wilt.  Place  them  in  an  oven  at  the 
temperature  of  about  110°  C.  and  dry  them  for  twelve  to 
twenty-four  hours.  Now  weigh  them  and  note  the  loss  in 
weight.  This  is  almost  entirely  due  to  the  evaporation  of  the 
water  in  the  leaf.  Calculate  the  percentage  of  water  in  the 
original  weight.  Repeat  the  experiment  with  various  parts  of 
the  same  plant  such  as  stems,  roots,  flowers,  fruit,  seeds,  etc., 
and  compare  the  amount  of  water  in  these  different  parts  as 
well  as  with  the  corresponding  parts  of  other  plants. 

(b)  To  demonstrate  imbibition  by  cell  walls,  take  a  measured 
block  of  wood  5  or  6  cm.  long  and  3  or  4  cm.  square.  Measure 
it  when  perfectly  dry,  i.e.  after  having  been  kept  a  day  or  two  in 
an  oven  at  110°  C.  Then  soak  it  in  water  (preferably  warm  or 
hot,  to  hasten  the  process).  Now  measure  accurately.  The 
piece  will  be  found  to  have  become  perceptibly  larger  owing  to 
the  imbibition  of  water  by  the  cell  walls.  Probably  the  first 
entrance  of  water  into  dry  seeds  is  also  due  to  imbibition  of 
water  by  the  cell  walls  and  protoplasm.  As  soon,  however,  as 
the  latter  has  imbibed  enough  to  become  hquid,  osmosis 
begins  to  act  also  in  the  taking  in  of  water. 


78  PLANT  PHYSIOLOGY 

(c)  Osmosis  may  be  demonstrated  by  tying  a  piece  of  fresh 
bladder  securely  across  the  mouth  of  a  thistle  tube  which  is 
inverted  and  filled  with  a  strong  solution  of  sugar  up  to  a  mark 
on  the  stem.  The  larger  end  with  the  bladder  is  now  placed 
in  a  dish  of  water  so  that  the  water  outside  stands  at  the  same 
height  as  the  water  inside.  The  water  will  enter  through  the 
bladder  by  osmosis  and  ascend  the  stem,  perhaps  reaching  a 
height  of  a  meter  or  more  above  the  level  of  the  water  outside. 
The  more  impermeable  the  membrane  is  to  the  substance  in 
solution  while  still  remaining  permeable  to  water,  the  greater 
the  difference  in  level  and  the  higher  the  pressure 
that  can  be  obtained.  The  latter  can  be  measured 
roughly  by  connecting  the  stem  of  the  thistle  tube  to 
a  mercury  manometer. 

(d)  The  relation  of  osmosis  to  turgor  may  be  demon- 
strated by  making  an  ''artificial  cell."  Fill  a  test 
tube  with  a  strong  sugar  solution  and  tie  a  piece  of 
bladder  firmly  over  the  open  end.  Place  in  a  dish  of 
water.  The  water  that  passes  into  the  tube  by  osmo- 
sis through  the  bladder  causes  the  latter  to  be 
stretched  and  to  bulge  out.  On  removing  the  tube  from  the 
water,  and  pricking  the  bladder  with  a  pin,  the  pressure 
developed  by  the  stretching  of  the  bladder  will  force  the  water 
out  in  a  stream. 

(e)  Mount  one  or  two  filaments  of  Spirogyra  in  water  and 
examine.  Measure  the  length  of  a  portion  including  a  definite 
number  of  cells.  Now  draw  a  2  per  cent,  potassium  nitrate 
solution  or  a  5  per  cent,  sugar  solution  under  the  cover  glass  by 
adding  it  at  one  side  and  withdrawing  the  water  from  the 
other  side  with  a  piece  of  filter  paper.  Measure  the  filament 
again.  Add  increasingly  strong  solutions  and  when  the  right 
strength  is  reached,  the  cytoplasm  will  be  found  to  be  drawing 
away  from  the  corners  of  the  cell  wall,  i.e.  plasmolysis  has 
begun.  This  indicates  that  with  the  withdrawal  of  water  by 
the  solution  outside,  the  much  stretched  cell  walls  have  lost 
their  tension  until  they  have  reached  a  state  in  which  they  are 
not  at  all  stretched.  As  the  water  is  still  withdrawn  from  the 
cell,  the  cytoplasm  is  pulled  further  and  further  away  from  the 
wall.  At  this  stage,  again  measure  the  fdament  and  calculate 
the  amount  that  the  turgid  filament  was  stretched. 

(/)  To  demonstrate  that  evaporation  from  a  membrane  filled 


LABORATORY  STUDIES  79 

with  water  has  a  strong  Hfting  power,  cover  the  end  of  a  thistle 
tube  tightly  with  a  piece  of  bladder  or  fill  the  mouth  with  a 
tightly  fitting  thin  layer  of  plaster  of  Paris.  Invert  the  tube 
and  fill  completely  with  water  that  has  been  boiled  to  remove 
the  air  so  that  bubbles  will  not  be  produced  in  the  tube.  Invert 
again  with  one  end  of  the  tube  in  a  dish  of  mercury.  Wet  the 
bladder  or  plaster  of  Paris  plug  externally.  As  evaporation 
progresses,  the  mercury  will  be  drawn  up  into  the  tube  until  a 
point  is  reached  where  the  pressure  of  air  on  the  outside  of  the 
bladder  or  plaster  of  Paris  is  sufficient  to  force  the  water 
back  out  of  it  so  that  it  is  no  longer  wet.  It  then  permits  air 
to  pass  through  rapidly  and  the  mercur}'-  soon  recedes  to  its 
original  level.  Similarly,  it  is  assumed  that  the 
evaporation  of  water  from  the  wet  cell  walls  into  the  O 
intercellular  spaces  of  the  leaves  exerts  a  strong  lift- 
ing power  on  the  water  in  the  stem  of  the  plant. 
This  will  be  shown  by  the  following  experiment. 

(g)  Cut  a  leafy  twig  and  fasten  it,  without  allow- 
ing the  cut  end  to  dry  out,  into  a  glass  tube  filled     fig.    -ti. 
with  water  and  with  its  lower  end  in  mercury.    This  — Evapora- 

/•I'lii  •  e  ''''"^  experi- 

expernnent,  if  successful,  will  also  show  a  rise  of  mer-  mem  (/). 
cury  in  the  glass  tube  as  in  the  preceding  one. 

(h)  Place  the  cut  end  of  a  stem  (preferably  a  herbaceous  one) 
in  a  strong  aqueous  solution  of  safranin.  After  an  hour  or  so, 
make  cross-sections  at  various  points.  The  colored  solution 
will  be  found  in  the  tracheary  tissue  (and  after  longer  standing 
also  in  some  of  the  immediately  surrounding  tissues,  especially 
in  wood  fibers). 

(i)  Place  a  branch  which  has  been  girdled  (i.e.  the  bark 
removed  to  but  not  including  any  of  the  wood)  with  its  lower 
end  in  water,  the  girdled  area  being  protected  from  drying  out 
by  coating  with  grafting  wax  or  paraffin.  Compare  with  a 
similar  branch  not  girdled.  Take  a  third  branch  and  through 
a  small  slit  in  the  bark  cut  off  the  wood  entirely  with  as  little 
injury  to  the  bark  as  possible.  Place  it  in  water  like  the  other 
two.  Note  the  differences  in  the  rapidity  of  wilting  in  the 
different  cases. 

(j)  Take  a  potted  plant,  e.g.  a  geranium  or  begonia,  and 
after  watering  it  well,  envelop  the  pot  in  a  sheet  of  rubber, 
tying  the  rubber  firmly  about  the  stem  of  the  plant.  Instead 
of  using  the  rubber,  the  outside  of  the  pot  and  the  top  of  the 


80  PLANT  PHYSIOLOGY 

soil  may  be  made  practically  water  proof  by  means  of  melted 
paraffin  whose  melting  point  is  sufficientl}''  low  so  as  not  to 
injure  the  stem  when  applied  to  the  top  of  the  soil  in  a  melted 
condition.  Weigh  the  pot  and  place  in  a  dry  room  for  an  hour 
and  weigh  again.  Calculate  the  loss  of  water  per  square 
centimeter  of  leaf  surface.  Place  in  a  moist  room  under  the 
same  light  conditions  as  before  and  note  the  loss  of  weight  in  an 
hour.  Such  experiments  are  not  accurate  as  many  factors 
enter  in  to  interfere,  but  they  give  an  idea  of  the  approximate 
amount  of  water  evaporated.  The  experiment  may  be 
continued  a  long  time  by  providing  an  opening  in  the  rubber  or 
paraffin  through  which  a  thistle  tube  passes  and  adding  every 
twenty-four  hours  as  much  water  as  was  lost  in  the  preceding 
2-4-hour  period.  By  keeping  a  record  in  this  way,  the  amount 
of  water  lost  in  a  week  can  be  determined  roughly.  (Of  course 
the  increase  in  weight  of  the  plant  itself  as  it  grows  is  a  factor 
not  taken  into  consideration  in  the  foregoing  nor  the  effect 
upon  the  roots  of  the  partial  exclusion  of  the  air  by  the  rubber  or 
paraffin.) 

(k)  To  show  that  it  is  mainly  through  the  stomata  that 
evaporation  (transpiration)  occurs,  take  three  lilac  leaves  of  as 
nearly  equal  size  as  possible.     Coat  the  ends  of  the  petioles  of 
each  and  the  under  surface  of  one  and  the  upper  surface  of 
another  leaf  with  a  varnish  made  of  equal  parts  of 
beeswax  and  lard  or  ordinary  grafting  wax  if  some- 
what softened.     Both  surfaces  of  the  third  leaf  are 
to  be  left  uncoated.    The  stomata  are  found  only  on 
the  lower  surface  and  it  will  be  found  that  the  leaf 
with  this  surface  coated,  thus  covering  the  stomata, 
remains  fresh  for  a  long  time  while  the  other  two 
wither  quickly. 
Fig.   42.       (A  'p^g  Icaves  of  the  Cottonwood  (Populus,  vari- 

— R    oot  •\i  ii-iVki 

pressure  ous  spccics)  havc  stomata  on  both  sides.  Repeat  the 
(Ji^f"™®'^^  foregoing  experiment  with  leaves  of  this  and  com- 
pare with  the  results  obtained  with  the  lilac, 
(m)  Root  pressure  may  be  demonstrated  by  cutting  off  the 
stem  of  a  rapidly  growing  sunflower  or  other  rather  large 
plant  (e.g.  tomato,  geranium,  castor  bean,  etc.)  and  slipping  a 
heavy  rubber  tube  over  the  cut  stump,  connecting  this  with  a 
narrow  glass  tube.  If  the  soil  be  kept  warm  and  wet  water  will 
soon  begin  to  escape  from  the  cut  surface  and  will  rise  to  a 


ENTRY  OF  SOLUTES  81 

considerable  height  in  the  tube.     If  the  latter  be  connected  with 
a  mercury  manometer  the  pressure  can  be  measured. 

116.  Nutrients  Other  than  Water.  All  other  sub- 
stances can  enter  the  plant  only  in  solution  in  water. 
This  is  true  of  the  gases  as  well  as  of  mineral  salts,  for 
although  a  gas  may  enter  the  air  spaces  of  a  leaf  in  the 
gaseous  state,  it  cannot  penetrate  the  wet  cell  walls  in  this 
state  but  must  go  into  solution.  It  is  then  subject  to  the 
same  physical  laws  of  diffusion  as  the  other  solutes. 

117.  The  wet  cell  wall  presents  no  (at  least  marked) 
obstacle  to  the  diffusion  of  any  solute.  The  plasma 
membrane,  however,  is  impermeable  for  some,  difficultly 
permeable  for  others,  and  easily  permeable  for  still  other 
substances.  Accordingly  the  molecules  of  the  substances 
in  solution  outside  of  a  cell  will  penetrate  into  the  cell 
with  different  degrees  of  rapidity  and  independent  of  the 
direction  that  the  water  is  passing.  The  result  will  be 
that  the  solution  inside  of  the  cell  may  have  its  compo- 
nents in  entirely  different  proportions  from  the  solution 
outside. 

118.  The  process  by  which  solutes  pass  into  the  cell 
and  from  cell  to  cell  is  diffusion.  This  is  the  molecular 
passage  of  a  solute  from  that  part  of  a  solution  where  the 
concentration  of  that  particular  solute  is  greater  to  where 
it  is  less.  As  long  as  the  plasma  membrane  is  easily 
permeable  for  the  particular  solutes  they  have  no  osmotic 
effect  and  may  diffuse  in  the  same  direction  with  or 
counter  to  the  osmotic  stream.  Thus  the  dissolved  salts 
that  enter  a  plant  do  so  independently  of  osmosis  and 
diffuse  toward  those  parts  of  the  plant  where  these 
particular  salts  are  less  abundant.  They  will  not 
become  more  concentrated  anywhere  in  the  plant  than 
outside  of  it  as  long  as  they  retain  their  same  composition 
and  the  permeability  of  the  plasma  membrane  remains 


82  PLANT  PHYSIOLOGY 

the  same.  Frequently,  however,  they  are  changed  chemi- 
cally after  they  enter  the  plant  and  then  are  no  longer  able 
to  pass  through  the  external  plasma  membrane.  In 
such  a  case  the  plant  may  be  able  to  take  in  large  amounts 
of  one  substance  from  a  dilute  solution.  Certain  sea- 
weeds, for  example,  accumulate  large  amounts  of  iodine 
compounds  from  the  sea  water  which  contains  iodides 
only  in  very  great  dilution. 

119.  Water  consists  of  hydrogen  and  oxygen  (H2O). 
Besides  these  two  elements  eight  others  are  ordinarily 
necessary  to  plant  life.  They  are  carbon  (C),  which 
chiefly  enters  the  plant  in  the  form  of  carbon  dioxide 
(CO2)  (see  paragraph  on  photosynthesis),  nitrogen  (N) 
in  the  form  of  nitrates  or  ammonium  salts,  calcium  (Ca), 
magnesium  (Mg)  and  potassium  (K),  these  mostly  oc- 
curring as  phosphates,  nitrates,  sulphates  or  carbonates, 
iron  (Fe)  in  very  small  amounts  as  salts  of  various  acids, 
sulphur  (S)  almost  entirely  as  sulphates  (except  in  those 
plants  that  feed  on  organic  food  where  it  may  be  taken  up 
from  the  proteins  and  a  few  lower  plants  which  use 
H2S  or  even  free  sulphur)  and  phosphorus  (P)  as  various 
phosphates.  In  addition  to  these,  sodium  (Na)  is  re- 
quired by  some  plants,  while  on  the  other  hand  calcium 
(Ca)  is  not  required  by  certain  fungi.  Of  the  ten 
elements  first  mentioned  the  last  seven  are  usually  taken 
in  as  mineral  salts  from  the  water  in  which  they  are 
dissolved.  The  oxygen  is  taken  in,  in  the  acid  radical  of 
the  sulphates,  nitrates,  carbonates  and  phosphates,  in 
combination  with  hydrogen  in  water,  and  in  combination 
with  carbon  in  carbon  dioxide  as  well  as  in  the  elementary 
form  directly  from  the  air  or  in  solution  in  the  water. 
Carbon  in  addition  to  being  taken  in  as  carbon  dioxide 
exists  in  the  carbonates  and  in  the  case  of  hysterophytes, 
also  in  various  organic  substances  taken  in  by  the  plant. 


ADDITIONAL  NUTRIENTS  83 

The   use   of  free  nitrogen   by   certain   bacteria,   will   be 
discussed  further  on. 

120.  In  addition  to  the  substances  mentioned  in  the 
preceding  paragraph,  silicon  (Si)  is  taken  up  by  many 
plants  (as  silicates  of  various  kinds)  and  adds  to  their 
hardness  but  can  be  dispensed  with  except  by  the 
diatoms  whose  cell  walls  are  composed  largely  of  silica. 
Sodium  can  take  the  place  of  potassium  for  many  pur- 
poses, e.g.  neutralizing  acids,  but  cannot  be  substituted 
for  it  entirely.  Similarly  an  excess  of  calcium  can  replace 
part  but  not  all  of  the  magnesium,  while  barium  (Ba)  and 
strontium  (Sr)  can  replace  part  of  the  calcium.  Chlorine 
(CI)  in  the  form  of  chlorides  is  useful  to  many  plants  but 
apparently  can  be  dispensed  with  by  almost  all.  The 
various  other  salts  present  in  the  soil  solution  may  be 
taken  up  by  the  plant  in  greater  or  less  degree,  but 
appear  either  to  have  no  use  whatever  or  to  be  used  only 
incidentally  without  being  indispensible.  Such  are  salts 
of  copper  (Cu)  aluminum  (Al)  manganese  (Mn)  zinc 
(Zn),  etc. 

121.  The  role  that  the  various  substances  mentioned 
in  the  foregoing  paragraphs  play  in  the  plant  economy 
is  not  certain  in  all  cases.  It  is  probable  that  calcium 
and  potassium,  perhaps  also  magnesium  and  iron,  are 
essential  parts  of  the  protoplasm  molecule.  Sulj)hur  is  a 
component  of  proteins  while  phosphorus  is  found  in  some 
proteins,  especially  in  the  nucleus.  Carbon,  hydrogen 
and  oxygen  are  the  components  of  the  carbohydrates 
which  are  the  chief  building  materials  of  the  plant  (e.g. 
cellulose)  and  of  the  proteins  out  of  which  protoplasm  is 
built  up.  In  the  absence  of  iron  the  chlorophyll  seems 
impossible  of  formation  although  it  does  not  contain  iron 
itself.  Mention  must  be  made  of  the  principle  of 
antagonistic  action  by  various  salts.     Thus  it  has  been 


84  PLANT  PHYSIOLOGY 

shown  that  solutions  of  certain  salts  poisonous  to  plants 
become  innocuous  upon  the  addition  of  certain  other 
salts  which  of  themselves  may  also  be  poisonous.  This 
discovery  has  thrown  doubt  upon  many  of  the  con- 
clusions of  earlier  botanists  as  to  the  functions  of  salts 
that  are  supposed  to  be  essential  to  plant  life. 

122.  So  far  we  have  merely  considered  what  sub- 
stances are  required  by  the  plant  and  something  of  the 
form  in  which  the  plant  takes  them  in.  Before  they  can 
be  used  they  must  undergo  various  decompositions  and 
recombinations;  in  other  words  after  absorption  there 
must  be  assimilative  processes.  Perhaps  the  most  funda- 
mental of  these  processes  is  that  by  which  the  carbon 
compounds  are  built  up  by  green  plants,  a  process  called 
photosynthesis. 

123.  Photosynthesis.  The  green  parts  of  all  chloro- 
phyll-bearing plants  absorb  carbon  dioxide  from  the 
surrounding  water  if  aquatic  plants,  or  from  the  air,  which 
contains  about  three  parts  of  it  to  ten  thousand.  This 
absorption  goes  on  only  when  the  plant  is  exposed  to  the 
light.  At  the  same  time  there  is  an  increase  in  the 
amount  of  carbohydrates  often  manifesting  itself  to  the 
eye  by  the  formation  of  starch  grains  in  the  chloroplasts, 
but  also  demonstrable  chemically  by  the  increased 
amount  of  sugars  (chiefly  glucose  C6H12O6)  in  the  cell 
sap.  At  the  same  time  it  can  be  demonstrated  that 
oxygen  is  given  off  by  the  plant.  It  is  this  process,  the 
manufacture  of  carbohydrates  by  green  plants  in  the 
presence  of  light,  that  has  received  the  name  photo- 
synthesis (from  the  Greek  meaning  ''putting  together 
by  light"). 

124.  Careful  experiments  have  shown  that  this 
process  cannot  occur  in  the  absence  of  any  one  of  the 
factors  mentioned  in  the  preceding  paragraph.     Thus  a 


PHOTOSYNTHESIS  85 

plant  growing  in  the  light  in  an  atmosphere  free  from 
carbon  dioxide  cannot  manufacture  carbohydrates  any- 
more than  if  it  were  in  the  dark.  A  plant  lacking  chloro- 
plasts,  e.g.  the  fungi,  cannot  manufacture  carbohydrates 
from  carbon  dioxide  even  if  light  be  present  (excepting  cer- 
tain bacteria,  the  so-called  nitrite  and  nitrate  bacteria). 
The  process  takes  place  in  the  chloroplasts  apparently. 
The  light  rays  most  effective  in  photosynthesis  seem  to  be 
those  in  the  red  part  of  the  spectrum  while  those  at  the 
violet  end  also  have  some  value.  Those  lying  between 
seem  in  the  main  to  be  useless.  The  green  color  represents 
the  portion  of  the  white  light  that  strikes  the  chlorophyll 
and  is  reflected  back  or  passes  through  it  without  being 
absorbed.  The  raw  materials  are  carbon  dioxide  and 
water,  the  energy  is  derived  from  the  absorbed  rays  of 
light  and  the  end  products  are  carbohydrates  and  oxygen. 

125.  The  exact  steps  in  photosynthesis  are  not 
certainly  known  but  the  following  seems  to  be  the 
probable  course  of  events: 

C02+H20  =  H2C03  (water,  plus  carbon  dioxide,  equals 
carbonic  acid). 

H2C03  =  H2CO  +  02  (carbonic  acid  acted  on  by  the 
energy  derived  from  light  by  the  cholorophyll  is  changed 
into  formaldehyde  and  oxygen) . 

6H2CO  =  C6Hi206  (formaldehyde,  probably  by  the 
aid  of  more  energy  derived  from  the  light  is  polymerized 
into  glucose). 

It  \\411  thus  be  seen  that  for  every  molecule  of  carbon 
dioxide  used  up  one  molecule  of  oxygen  (O2)  will  be  set 
free.  Glucose  is  the  carbohydrate  first  formed  in  most 
cases  but  as  this  accumulates  in  the  chloroplasts  and 
cell  sap  it  is  often  transformed  rapidly  into  the  insoluble 
starch  (C6Hio05)n  which  becomes  stored  up  in  large 
quantities  in  the   chloroplasts.     Sometimes  instead  of 


86  PLANT  PHYSIOLOGY 

starch,  drops  of  oil  are  produced  in  the  cytoplasm  and 
cell  sap,  or  cane  sugar  (C12H22O11)  or  some  other 
carboliydratcs. 

126.  The  further  fate  of  the  carbohydrates  formed  in 
photosynthesis  is  varied.  The  excess  of  glucose  or  other 
sugars  in  the  chlorophyll-bearing  cells  in  addition  to 
what  is  put  aside  temporarily  in  insoluble  form  as  starch 
diffuses  through  the  adjacent  cells  and  finally  reaches 
the  vascular  bundles  where  it  enters  the  parenchyma  cells 
bordering  the  sieve  tubes.  It  probably  diffuses  through 
these  into  the  latter  in  which  it  diffuses  and  is  probably 
also  carried  by  streams  of  protoplasm  to  those  parts  of 
the  plant  where  the  tissues  contain  less  glucose. 
Here  it  diffuses  out  into  these  tissues.  Besides  passing 
in  the  sieve  tissues  diffusion  doubtless  occurs  from  cell 
to  cell  throughout  the  parenchyma  of  the  cortex  espe- 
cially in  those  cells  bordering  on  the  sieve  tubes.  Dur- 
ing the  night  the  starch  grains  that  have  accumulated 
in  the  chloroplasts  in  day  time  are  transformed  into 
glucose  which  diffuses  in  the  manner  just  described. 

127.  The  carbohydrates  transported  in  this  manner 
may  be  stored  up  as  reserve  food  in  various  forms.  Thus 
they  may  be  transformed  into  starch  in  the  leucoplasts  of 
the  storage  organs,  e.g.  tubers  of  potato,  roots  of  sweet 
potato  {lyomoea  batatas),  pith  of  various  twigs  such 
as  apple,  sassafras,  etc.,  medullary  rays  of  many  trees, 
endosperm  or  cotyledons  of  seeds,  etc.  Cane  sugar  may 
be  found  in  many  plants  such  as  beets,  maple,  sugar  cane, 
etc.  Inulin  is  found  in  the  roots  of  many  plants  par- 
ticularly those  belonging  to  the  order  Asterales.  Trans- 
formed into  fats  they  are  found  in  many  seeds,  e.g.  flax, 
cotton,  peanut,  castor  bean,  as  well  as  in  the  bulb  scales 
of  onion,  leaves  of  cabbage,  etc.  In  the  seeds  of  many 
palms,  e.g.  date,  and  the  wood  of  many  trees,  e.g.  elm  and 


PROTEIN  SYNTHESIS  87 

mulberry,  the  reserve  carbohydrate  is  in  the  form  of  a 
thick  deposit  on  the  inner  surface  of  the  cell  wall.  This 
is  a  substance  closely  related  to  cellulose,  one  of  the  hemi- 
celluloses.  The  sugars  in  fruits  perhaps  belong  in  the 
category  of  stored  foods  although  they  serve  rather  as 
a  bait  for  animals  which  on  eating  the  fruit  aid  in  the 
distribution  of  the  seeds. 

128.  The  carbohydrates  produced,  whether  first 
stored  up  or  used  immediately,  have  for  their  ultimate 
destination  various  functions.  As  building  materials 
they  are  used  up  in  the  formation  of  cell  walls  in  the  grow- 
ing parts  of  plants.  Whether  they  are  thus  used  directly 
or  must  first  become  a  part  of  the  protoplasm  is  uncertain. 
The  use  of  carbohydrates  in  furnishing  energy  to  the 
plant  will  be  discussed  under  the  topic  Respiration. 

129.  A  considerable  portion  of  the  carbohydrates 
eventually  becomes  built  up  into  those  very  complex 
nitrogenous  compounds  called  proteins.  Whether  the 
carbohydrates  are  taken  as  such  and  combined  with 
nitrogen  obtained  from  the  nitrates  and  sulphur  and 
phosphorus  from  the  sulphates  and  i:)hosphates  re- 
spectively, the  product  being  proteins,  or  whether  as 
seems  possibly  may  be  the  case  part  of  them  are  broken 
down  and  then  combined  with  the  nitrogen  to  form 
hydrocyanic  acid  (HCN)  this  being  polymerized  and 
combined  with  other  carbohydrate  molecules  and  with 
sulphur  and  i)hosphorus,  is  not  known.  In  any  case 
hydrocyanic  acid  is  often  formed  in  i:>lants  in  which  active 
protein  production  is  taking  i)lace. 

130.  Certain  bacteria,  chiefly  parasitic  in  the  roots 
of  plants  of  the  bean  family  (Fabaceae),  are  capable, 
when  supplied  with  carbohydrates  and  the  necessary' 
mineral  salts,  of  using  the  atmospheric  nitrog(>n  (as  dis- 
solved in  the  soil  water)  in  building  up  protein  com- 


88  PLANT  PHYSIOLOGY 

pounds.  These  bacteria  form  galls  on  the  roots  of  the 
host  plants.  As  they  grow  old  the  host  plant  digests 
them  and  is  thus  able  to  thrive  in  a  soil  free  from  nitrog- 
enous compounds.  Thus  if  the  bacteria  are  present, 
crops  of  beans,  clover,  alfalfa,  etc.  will  actu- 
ally increase  the  amount  of  nitrogenous 
compounds  in  the  soil  instead  of  decreas- 
ing it. 

131.  The  proteins  formed  may  be  stored 
up  as  such  for  future  use  by  the  plant  (e.g. 
aleuron  in  seeds)  or  may  be  transported  to 
those  parts  of  the  plant  where  new  cell 
■^SdulermcL')  *  production  and  growth  are  taking  place. 
Here  it  is  built  up  into  protoplasm.  How 
this  is  accomplished  we  do  not  know.  The  path  of 
transportation  seems  to  be  in  the  sieve  and  possibly 
laticiferous  tissues.  The  form  in  which  protein  matters 
are  transported  may  be  either  as  simple  proteins  or  as 
amids. 

132.  Hysterophytic  plants,  i.e.  plants  that  lack  chloro- 
phyll, must  obtain  their  organized  food  (carbohydrates, 
proteins,  fats,  etc.)  from  sources  outside  of  themselves. 
We  find  all  degrees  of  ability  to  make  use  of  various 
food  sources.  Some  hysterophytes  simply  require 
carbohydrates  and  mineral  salts  and  can  produce  their 
own  proteins,  others  must  have  special,  and  in  the  case 
of  parasites,  living  forms  of  proteins.  Some  even  are 
able  to  use  simpler  carbon  compounds  than  carbohy- 
drates such  as  some  of  the  simpler  organic  acids,  glycer- 
ine, etc.  In  general,  however,  the  nutrition  of  hystero- 
phytes differs  but  little  from  that  of  holophytes  (i.e. 
plants  containing  chlorophyll)  except  in  their  inabihty 
to  manufacture  their  own  carbohydrates. 

133.  The    means    by    which    hysterophytic    plants 


NUTRITION  OF  HYSTEROPHYTES  89 

obtain  their  food  supplies  are  quite  varied.  One-celled 
plants  like  yeasts  and  bacteria  absorb  the  organic  sub- 
stances directly,  or  often  decompose  them  to  the  appro- 
priate form  by  means  of  digestive  ferments  called 
enzymes,  which  are  organic  compounds  of  complex 
structure  whose  exact  action  is  not  clearly  known.  Fungi 
consist  of  long  filaments  of  cells  which  either  pass 
through  the  substances  to  be  absorbed  or  send  little 
suckers,  called  haustoria,  into  the  cell  of  the  host,  the 
latter  being  often  the  case  with  fungi  i)arasitic  upon 
living  plants.  Among  the  hysterophytic  flowering  plants 
some  feed  on  decayed  organic  matter  in  the  soil,  others, 
e.g.  dodder,  send  haustoria  into  living  plants,  and  take 
organic  substances  directly  from  them.  Some  of  the 
mistletoes  which  possess  chlorophyll  take  little  else  than 
water  and  mineral  salts.  Of  especial  interest  are  the 
insectivorous  plants  which  catch  and  digest  insects  by 
means  of  special  structures.  The  digested  insects  are 
the  source  of  their  nitrogen  for  many  of  these  plants  that 
hve  where  nitrogen  compounds  are  lacking  in  the  soil. 
Some  plants  have  fungous  hyphae  growing  partly  within 
and  partly  outside  of  some  or  all  of  their  roots.  Such  roots 
are  often  of  peculiar  shape  and  are  known  as  mycorrhiza. 
The  fungi  absorb  water  and  mineral  salts  from  the  soil 
and  deliver  them  to  the  root  from  which  in  turn  they 
take  organic  foods.  Some  of  these  fungi  are  said  to  be 
able  to  make  use  of  the  atmospheric  nitrogen  as  do  the 
bacteria  in  the  root  tubercles  of  the  bean  family. 

134.  All  the  foregoing  processes,  e.g.  transformation  of 
carbohydrates  from  one  form  to  another,  their  trans- 
portation and  storage,  their  ])uilding  uj)  into  proteins, 
the  transportation  and  storing  away  of  the  latter  and 
their  building  up  into  protoplasm,  require  the  expenditure 
of   a   considerable    amount   of   energy.     This   must   be 


90  PLANT  PHYSIOLOGY 

available  in  every  living  cell  and  not  confined  to  any 
definite  locality  in  the  plant.  This  is  made  available  by 
the  process  known  as  respiration. 

135.  Respiration.  With  the  exception  of  a  few 
bacteria  and  low  fungi  to  be  mentioned  later  all  living 
cells  absorb  oxygen  and  give  off  carbon  dioxide,  the 
process  being  accompanied  by  a  loss  in  weight.  In 
green  plants  in  the  light  the  absorption  of  carbon  dioxide 
and  giving  out  of  oxj^gen  are  so  much  greater  than  this 
other  process  that  for  years  it  was  not  known  that  the 
latter  takes  place.  It  is  not  dependent  upon  the 
presence  of  light  nor  are  chloroplasts  necessary  for  its 
occurrence.  It  takes  place  more  rapidly  the  higher  the 
temperature  until  an  optimum  temperature  is  reached 
which  is  sometimes  perilously  near  to  the  death  point  of 
the  cell. 

136.  The  oxygen  is  taken  from  the  air  (which  contains 
nearly  20  per  cent,  of  oxygen)  by  the  aerial  parts  of  the 
plant.  It  passes  through  the  stomata  and  lenticels  and 
also  to  some  extent  through  the  cuticle  into  the  inter- 
cellular spaces  and  from  thence  is  absorbed  by  the 
cells.  The  roots  whose  outer  walls  are  only  slightly 
cutinized  and  whose  root  hairs  are  practically  free  from 
cutin  absorb  the  oxygen  which  is  dissolved  in  the  soil 
water  and  which  is  present  in  the  air  spaces  between 
the  soil  particles.  Submerged  plants,  e.g.  algae,  absorb 
the  oxygen  dissolved  in  the  water.  Many  trees  which 
grow  in  swamps  where  the  soil  lacks  oxygen  send  up 
peculiar  vertical  branches  from  their  roots  out  to  the 
surface  and  up  into  the  air,  these  serving  as  aerating 
organs  for  the  roots.  Such  are  the  ''knees"  of  the 
bald  cypress  {Taxodium  distichum)  when  the  latter 
grows  in  wet  places  (and  which  are  lacking  when  it  grows 
in  well  aerated  soil)  and  the  aerial  roots  of  sotne  of  the 


RESPIRATIOX  91 

mangroves  (e.g.  the  black  mangrove  of  Florida,  Avicen- 
nia  nitida). 

137.  Respiration  consists  primarily  in  the  breaking  up 
of  the  complex  molecules 'of  certain  organic  compounds 
(chiefly  car])oh3'drates  or  even  the  carbohydrate  portions 
of  protoplasm  molecules)  into  simpler  compounds.  This 
releases  a  large  amount  of  energy  much  of  which  becomes 
available  for  the  use  of  the  plant.  Since  all  living  parts 
of  the  plant  require  energy,  respiration  will  be  found  to 
take  place  in  all  parts.  The  intensity  of  the  respiration 
varies  with  many  factors,  viz.  the  amount  of  food  avail- 
able that  can  be  broken  down  into  simpler  compounds, 
the  availability  of  oxygen,  the  amount  of  water,  the 
temperature,  etc.  To  what  extent  the  protoplasm  itself 
can  regulate  the  occurrence  of  this  process,  if  the  other 
conditions  are  fulfilled,  is   uncertain. 

138.  Part  of  the  energy  set  free  in  respiration  is 
exhibited  in  the  form  of  heat.  This  is  especially  notice- 
able where  rapid  gro^\i3h  and  rapid  respiration  are  oc- 
curring as  in  large  flower  buds,  fruiting  bodies  of  large 
fungi,  etc.  In  ordinary  parts  of  plants  the  radiating 
surface  is  great  enough  to  keep  the  plant  cool  so  that  the 
heating  is  not  noticeable.  In  the  case  of  wet  leaves,  hay, 
manure,  etc.,  the  heat  produced  by  the  respiratory  proc- 
esses of  the  fungi  and  especially  the  bacteria  present 
leads  in  some  cases  to  the  kindling  of  some  of  the  easily 
inflammable  substances  produced  so  that  it  is  a  frequent 
occurrence  for  hay,  especially  moist  alfalfa  hay,  and 
manure  to  catch  fire. 

139.  It  has  been  shown  that  there  are  two  distinct 
stages  in  respiration  which  follow  one  another  so  closely 
in  most  cases  that  they  a])pear  as  one.  These  are  the 
anaerobic  and  aerobic  stages.  Certain  bacteria  and 
yeasts  show  only  the  first  stage.     In  this  stage  no  oxygon 


92  PLANT  PHYSIOLOGY 

is  required  from  outside  the  ceU.  By  the  aid  of  certain 
enz3^mes  produced  by  the  cell  the  carbohydrates  or  other 
substances  used  in  respiration  are  started  in  their  disin- 
tegration and  proceed  in  it  until  simpler  compounds  and 
some  carbon  dioxide  are  produced.  Thus  glucose  is  usually 
decomposed  into  alcohol  and  car])on  dioxide,  the  end 
results  being  in  accordance  with  the  following  formula: 

C6H12O6-2C2H5OH+2CO2. 

It  is  probable  that  the  reaction  is  not  as  simple  as  this, 
but  that  there  are  many  steps  in  the  process.  This  proc- 
ess sets  free  a  certain  amount  of  energy.  In  the  produc- 
tion of  alcohol  and  carbon  dioxide  from  sugar  by  the  yeast 
plant  it  is  this  anaerobic  stage  of  respiration  that  takes 
place.  Corresponding  decomposition  processes  occur  in 
various  kinds  of  bacterial  fermentation  and  decay,  the 
intermediate  and  end  products  varying  with  the  com- 
position of  the  substance  fermented  and  the  kind  of 
organism. 

140.  The  aerobic  stage  consists  usually  of  the  oxid- 
ation of  the  rather  complex  compounds  produced  in  the 
anaerobic  stage  to  simpler  compounds,  this  also  being 
accompanied  by  the  liberation  of  energy  in  large 
amounts.  This  process  also  is  probably  carried  on  by 
the  aid  of  enzymes  and  it  may  be  that  the  use  of  the 
oxygen  is  rather  to  get  rid  of  harmful  products  instead 
of  being  the  agent  which  sets  free  the  energy.  Taking 
the  case  illustrated  in  the  preceding  paragraph  the 
alcohol  is  broken  down  and  combined  with  oxygen  to 
form  carbon  dioxide  and  water.  The  final  results,  but 
not  the  intermediate  stages,  are  shown  by  the  following 
formula 

C2H5OH+6O  =  2CO0+3H2O. 
Alcohol + oxygen  =  carbon  dioxide  +  water. 


RESPIRATION  93 

By  comparing  the  final  results  of  the  anaerobic  and  aero- 
bic respiration  of  glucose  with  the  steps  in  the  photo- 
synthetic  production  of  glucose  we  realize  that  the  proc- 
esses are  the  reverse  of  one  another.  It  is  reasonable 
to  suppose  then  that  the  amount  of  energy  set  free  in 
the  processes  of  respiration  will  equal  that  required  to 
build  up  the  same  amount  of  glucose  in  photosynthesis. 
Viewed  from  this  standpoint  respiration  is  the  process 
by  which  the  plant  obtains  at  the  places  where  it  is  needed 
the  energy  taken  in  from  the  light  by  the  chloroplasts. 
The  manufacture  by  photosynthesis  of  an  excess  of 
carbohydrates  over  that  used  each  day  by  the  plant  in 
respiration  enables  the  plant  to  store  up  a  large  amount 
of  energy  for  the  winter  season  when  photosynthesis 
cannot  occur  or  for  the  rapid  grow^th  of  new  organs 
another  season.  With  all  the  processes  of  respiration 
the  protoplasm,  the  living  part  of  the  cell,  is  intimately 
connected.  It  is  to  it  that  the  energy  set  fr^e  is  probably 
transferred.  It  is  apparently  the  protoplasm  that  regu- 
lates the  amount  and  location  of  the  respiratory  activi- 
ties. How  all  this  is  brought  about  is  still  unknown  as 
is  the  relation  of  the  structure  of  protoplasm  and  the 
energy  used  to  what  we  call  ''life." 

141.  In  place  of  the  type  of  respiration  described 
above  a  few  bacteria  obtain  their  energy  in  other  ways. 
Thus  the  nitrite  bacteria  oxidize  the  ammonia  of  am- 
monium salts  to  nitrites  and  the  nitrate  bacteria  oxidize 
the  nitrites  to  nitrates,  each  of  these  processes  setting 
free  a  small  amount  of  energy  which  is  made  use  of  by 
the  bacteria.  In  both  cases  the  energy  thus  obtained  is 
sufficient  to  enable  the  cells  to  build  up  from  carbon 
dioxide  and  water  the  carbohydrates  needed  in  the 
cell's  growth  and  further  to  combine  these  with  the  nec- 
essary   substances    to    form    proteins    and    protoplasm. 


94  PLANT  PHYSIOLOGY 

Still  other  bacteria  inhabiting  sulphur  springs  or  places 
where  sewage  is  abundant  obtain  the  necessary  energy 
by  oxidizing  US  to  SO2,  sulphur  frequently  being  stored 
up  as  a  reserve  food  supply.  It  is  held  by  some  investi- 
gators that  other  bacteria  obtain  their  energy  by  oxi- 
dizing certain  iron  compounds,  others  by  oxidizing 
methane  and  still  others  hydrogen. 

142.  In  the  foregoing  processes  of  photosj^nthesis 
and  respiration  (including  fermentation)  many  other 
substances  are  produced  besides  those  mentioned.  Some 
of  these  are  perhaps  nothing  more  than  waste  products, 
or  at  least  by-products,  but  others  are  reserve  food  of 
various  kinds.  Still  others  perhaps  serve  for  special 
functions  such  as  protection  of  plants  from  attacks  of 
insects,  covering  of  wounds,  etc.  Among  the  substances 
thus  produced  and  whose  functions  are  not  certainly 
known,  are  the  alkaloids  of  which  a  great  many  have  been 
studied,  e.g.  caffein,  nicotine,  etc.  Besides  these  may  be 
mentioned  resins,  rubber,  gutta-percha,  glucosides,  etc. 
Many  of  these  are  of  great  use  to  man.  Many  are  very 
poisonous.  The  organic  acids  mostly  stand  in  another 
category.  They  are  either  directly  reserve  stuffs,  re- 
placing carbohydrates,  or  are  stages  in  the  respiration 
of  carbohydrates,  or  in  many  cases  are  the  substances 
which  produce  the  requisite  osmotic  pressure  within  the 
cell.  The  commonest  organic  acids  are  the  following: 
maUc,  (C4H6O5)  found  in  the  apple  and  many  other 
fruits  as  well  as  in  the  leaves  of  many  succulent  plants, 
citric  (CeHsO?)  in  the  fruits  of  lemon,  orange,  etc., 
tartaric  (C4H6O6)  in  fruit  of  grapes,  oxalic  (C2H2O4) 
in  the  leaves  of  many  plants,  e.g.  Oxalis,  Rumex,  etc., 
and  tannic  acid  (C14H10O9)  and  its  derivatives  which  ap- 
pear to  play  a  very  important  but  little  understood  part 
in  the  energy  relations  of   the   plant.     ]\Iany  of  these 


TEMPERATURE  95 

acids  are   present  in  the  free  form   but  some  of  them 
appear  mostly  as  the  acid  salts  of  various  metals. 

143.  Temperature.  The  relation  of  the  plant  to 
temperature  will  be  discussed  here  as  it  is  chiefly  a  ques- 
tion of  the  effect  of  temperature  upon  the  nutritive 
functions.  Five  cardinal  points  for  temperature  can  be 
distinguished  for  these  different  processes.  They  are: 
death  point  from  cold,  death  point  from  heat  (points 
which  are  the  same  whatever  the  process  and  mentioned 
here  simply  because  when  reached  the  process  cannot 
be  resumed  when  normal  temperatures  are  again  re- 
gained), minimum,  optimum  and  maximum.  The  last 
three  are  quite  different  for  different  life  processes. 
Thus  the  optimum  and  maximum  for  respiration  are 
usually  much  higher  than  for  photosynthesis,  in  fact 
they  often  lie  close  to  the  death  point  from  heat.  Be- 
tween the  death  point  from  cold  and  the  minimum  for 
various  processes  may  be  a  small  range  or  sometimes 
a  great  range  of  temperature.  Usually  the  minimum 
point  is  a  little  above  or  not  much  below  0°  C.  The 
maximum  temperature  for  the  various  functions  lies 
usually  between  36°  and  43°  C.  and  the  death  point  be- 
tween 50°  and  55°  C,  but  in  a  few  plants  of  hot  springs 
as  well  as  some  bacteria  causing  the  heating  of  manure, 
etc.,  the  optimum  temperature  may  be  about  60°  and 
the  death  point  even  as  high  as  75°  to  85°  C. 

144.  The  death  of  plants  by  heat  appears  to  be  due 
to  the  coagulation  of  some  of  the  protein  constituents  of 
the  protoplasm.  Since  this  coagulation  cannot  occur 
unless  a  certain  amount  of  water  is  present  we  find  that 
some  nearly  water-free  structures  are  able  to  endure 
rather  high  temperatures.  Thus  the  spores  of  some 
bacteria  can  be  boiled  for  several  hours  before  they  are 
killed  and  some  seeds  can  endure  a  dry  heat  exceeding 


96  PLANT  PHYSIOLOGY 

100°  C.  Similarly  dry  plant  parts  can  endure  very  low 
temperatures.  Many  seeds  are  not  killed  by  an  ex- 
posure for  several  hours  to  the  temperature  of  liquid 
hydrogen  (below  —  250°  C).  The  latter  is  also  true  for 
many  single-celled  water  plants  that  must  contain  plenty 
of  water,  e.g.  diatoms,  bacteria,  etc.  On  the  other  hand 
many  watery  tissues  are  killed  by  a  temperature  that  does 
not  reach  the  freezing  point.  Just  the  reason  for  this  is 
unknown.  It  is  here  suggested  that  at  these  low 
temperatures  certain  processes  continue  which  result  in 
the  accumulation  of  poisons,  while  the  processes  that 
would  usually  destroy  these  poisons,  are  prevented  by  the 
low  temperature  so  that  in  reahty  the  death  of  the  plant 
would  be  due  to  poisoning. 

145.  Freezing  of  plants  may  cause  death  in  several 
ways:  (1)  the  ice  crystals  formed  may  rupture  the 
cells  or  disrupt  the  tissues;  (2)  the  water  may  escape 
into  the  intercellular  spaces  and  be  frozen  there  and  on 
thawing  rapidly  may  remain  outside  the  cells  filling  up 
the  intercellular  spaces  and  cutting  off  the  air  supply; 
(3)  the  withdrawal  of  water  from  the  protoplasm  by  freez- 
ing may  so  increase  the  concentration  of  certain  sub- 
stances dissolved  in  the  cell  sap  that  the  cells  are  killed. 
Upon  the  whole  subject  considerable  uncertainty  rests. 

146.  Effect  of  Poisons.  Many  substances  are  poison- 
ous to  living  plant  cells.  The  effects  are  almost  as  varied 
as  the  types  of  poisons.  Some,  like  the  strong  acids, 
simply  decompose  the  protoplasm  and  cell  walls  and  so 
destroy  life;  others,  Hke  the  salts  of  the  heavier  metals, 
coagulate  the  protoplasm;  others  even  in  minute  quanti- 
ties interfere  with  the  nutrition  of  the  cell  in  a  manner 
not  understood,  and  kill  it.  Thus  one  part  of  copper  in 
ten  million  parts  of  water  will  kill  certain  algae  and  fungi. 
Hydrocyanic  acid   acts  apparently  by  preventing  the 


EFFECT  OF  POISONS  97 

taking  in  or  using  of  oxygen  in  respiration.  IMany 
parasitic  plants,  e.g.  bacteria  and  fungi  secrete  poisons 
or  induce  activities  in  the  cells  of  the  host  that  lead  to  the 
accumulation  of  poisons  that  may  destroy  the  life  of  a 
cell  or  lead  it  to  abnormal  growth  or  functioning. 

Laboratory  Studies,  (a)  Take  a  piece  of  the  root  of  a  living 
red  beet.  Cutout  a  cube  a  centimeter  or  so  in  diameter.  Wash 
off  the  colored  cell  sap  that  has  escaped  from  the  cut  cells  and 
place  the  cube  in  a  test  tube  of  water.  So  long  as  the  cells  are 
alive  their  plasma  membranes  prevent  the  colored  solute  in  the 
cell  sap  from  escaping.  Gently  heat  the  test  tube.  When  the 
death  point  of  the  beet  tissues  is  reached  (below  G0°  C.)  the 
plasma  membranes  are  no  longer  impermeable  and  the  color 
diffuses  out  into  the  surrounding  water.  This  experiment  also 
shows  that  the  cell  walls  themselves  are  but  slight  obstacles 
to  diffusion.  Instead  of  by  heating,  similar  results  may  be 
obtained  by  using  certain  poisons  such  as  strong  alcohol,  etc., 
but  care  must  be  taken  not  to  choose  a  substance  that  will 
destroy  the  coloring  matter. 

(b)  Set  up  a  series  of  water  cultures  as  follows :  Take  glass 
jars  (]\Iason  jars  will  do)  and  to  keep  the  contents  dark  encase 
each  with  a  cylinder  of  pasteboard  which  can  be  removed  to 
permit  of  observation.  Fill  these  jars  nearly  full  of  the  solution 
to  be  tested,  leaving  a  small  air  space  between  the  water  and 
the  cork.  The  cork  should  have  at  the  center  a  hole  5  or 
6  mm.  in  diameter.  Germinate  some  peas,  corn,  buckwheat  or 
mustard  seeds.  When  the  radicles  are 2  to  3  cm.  long,  fasten 
one  seed  to  each  cork  in  such  a  way  that  the  root  just  enters  the 
solution  and  the  plumule  is  in  a  position  to  pass  uj)  through  the 
hole  in  the  cork  (or  the  seed  can  be  fastened  outside  with  the 
root  passing  through  the  hole).  Instead  of  a  cork  the  jars  may 
be  nearly  filled  with  water  and  melted  parafhn  poured  upon  it ; 
after  the  paraffin  has  hardened  several  holes  may  be  made 
through  it  by  means  of  a  hot  metal  rod.  The  water  can  now 
be  poured  out  and  the  desired  liquid  poured  in,  nearly  up  to  the 
under  side  of  the  paraffm.  The  germinated  seeds  can  be  set 
upon  this  paraffin  cap  in  such  a  way  that  the  radicles  will  pass 
throu2;h  the  holes.  Expose  all  the  jars  to  the  same  light  and 
temperature  so  that  as  far  as  possible  the  only  differences  will 

7 


98  PLANT  PHYSIOLOGY 

be  those  of  the  composition  of  the  solutions.  Make  up  the 
following  solutions  and  fill  into  the  jars: 

1.  Distilled  water 

2.  Complete  culture  solution  (Sachs) 

3.  Complete  culture  solution,  omitting  the  KNO3 

4.  Complete  culture  solution,  omitting  the  ]\IgS04 

5.  Complete  culture  solution,  omitting  the  KXO3  and 

K2SO4  and  adding  Ca(N03)2  in  place  of  the  first. 

6.  Complete  culture  solution,  omitting  theCa3(P04)2 

and  adding  an  equal  amount  of  Ca(N03)2 

7.  Complete  culture  solution,  omitting  theK2S0i  and 

MgS04  and   replacing  by  an  equal  amount  of 
Mg(N03)2 

8.  Complete  culture  solution  omitting  the  Ca3(PO.i)2 

and  substituting  K2HPO4 

9.  Complete  culture  solution  omitting  the  FeCU. 
The  Sachs'  solution  consists  of: 

Distilled  water 1000      cc. 

KNO3 1      gm. 

K2SO. 0.5  gm. 

MgS04 0.4  gm. 

Ca3(PO02 0.5  gm. 

FeCls trace. 

Let  the  plants  grow  for  several  weeks,  rej^lacing  the  old 
solutions  by  fresh  ones  of  the  same  composition  every  week  or 
so.  Compare  the  amount  of  growth  of  both  roots  and  stems  in 
the  different  solutions,  the  size  and  color  of  the  leaves,  etc. 
Note  when  growth  ceases  and  to  what  stage  of  development 
the  plant  proceeds  before  its  death. 

(c)  Bring  some  Spirogyra  into  the  laboratory  and  place 
in  a  dark  room  (not  too  cold)  for  twentj'-four  to  thirt^^-six 
hours  or  until  on  testing  some  of  the  plants  with  iodine  solution 
no  starch  is  found.  Bring  the  dish  into  the  sunlight  and  with 
iodine  solution  test  some  of  the  plants  for  starch  after  five 
minutes,  ten  minutes,  half  an  hour,  etc. 

(d)  In  a  rather  broad,  deep  glass  dish  (e.g.  a  wide  battery 
jar)  place  some  actively  growing  Spirogyra.  Put  a  bit  of  wire 
netting  (iron,  not  copper  nor  brass)  into  the  bottom  of  a  short- 
tubed  funnel  and  invert  over  the  Spirogyra  submerging  the 


LABORATORY  STUDIES  99 

funnel  and  its  tube  completel}'.  Over  the  latter  invert  a  test 
tube  filled  with  water.  Now  raise  the  funnel  as  high  as  it  will 
go  without  lifting  the  edge  of  the  test  tube  above  the  surface 
of  the  water,  supi)orting  it  on  a  small  block.  Place  the  whole 
in  the  sunlight.  As  photosynthesis  goes  on  the  oxygen  given  off 
by  the  pond  scum  collects  in  the  test  tube  and  may 
be  tested  in  various  ways,  e.g.  by  carefully  re- 
moving the  test  tube,  inverting  it  and  inserting 
a  glowing  splinter  which  will  burst  into  flame  if 
sufficient  oxygen  is  present.  The  diameter  of  the 
funnel  must  be  considerably  less  than  that  of  the 
jar  or  no  CO2  can  reach  the  Spirogyra  and  photo- 
synthesis will  soon  cease.  If  CO 2  is  passed  into 
the  water  occasionally,  taking  care  not  to  let  any 
bubbles  enter  the  funnel,  the  activity  of  the  process 
is  increased. 

(e)  In  a  similar  way  the  oxygen  evolved  in  photosynthesis  by 
Philotria  (Elodea)  may  be  collected  by  inserting  the  cut  ends  of 
several  plants  into  the  mouth  of  an  inverted  test  tube  filled 
with  water  and  placing  the  whole  dish  in  the  sunlight.  Care 
must  be  taken,  however,  not  to  confuse  two  phenomena  here,  viz. 
the  rapid  outflow  of  bubbles  at  first,  due  to  the  expansion  of  the 
gas  already  present  in  the  stem  as  it  heats,  and  the  much  slower 
evolution  of  oxygen  by  photosj-nthesis.  After  the  first  outrush 
of  gas  due  to  the  expansion  by  heat  is  past  the  relative 
amount  of  photosynthesis  can  be  told  with  a  fair  degree  of 
accuracy  by  counting  the  number  of  bubbles  of  oxygen  evolved 
per  minute  under  the  different  conditions.  Be  sure,  however, 
to  keep  the  water  well  supplied  with  CO2.  Test  now  the  effect 
of  placing  glass  plates  of  difi"erent  colors  in  front  of  the  dish 
containing  this  j)lant,  in  all  cases  waiting  long  enough  to 
avoid  the  effect  of  the  changing  volume  of  the  enclosed  gas  due 
to  changes  of  temperature. 

(/)  Place  two  potted  geranium  (Pehirgonium)  ]ilants.  prefer- 
ably with  plain,  not  variegated  leaves,  in  the  dark  until  their 
leaves  contain  no  starch.  Now  place  them  under  bell  jars, 
sealing  one  air  tight  with  sealing  wax  or  by  other  means,  first 
placing  under  the  jar  a  dish  containing  a  strong  solution  of 
KOH  to  absorb  all  CO2.  Leave  a  small  air  space  under  the 
edge  of  the  other  bell  jar  so  as  to  permit  the  entry  of  air 
containing  CO2.     After  an  hour  or  so  place  both  plants  in  the 


100  PLANT  PHYSIOLOGY 

sunlight  and  after  three  or  four  hours  test  their  leaves  for  the 
presence  of  starch  as  follows:  Remove  a  leaf,  immerse  it  in 
hot  alcohol  for  a  few  minutes  to  extract  the  chloro])hyll  and  then 
cover  with  a  strong  solution  of  iodine  which  will  color  the  leaf 
blue  or  not  according  as  the  starch  is  present  or  absent.  To 
avoid  rupture  of  the  sealing  by  the  expanding  air  it  is  well  to 
use  a  bell  jar  with  an  opening  at  the  top  into  which  is  placed  a 
cork  through  which  a  glass  tube  passes.  This  tube  should  be 
bent  so  that  its  other  end  is  immersed  in  a  dish  of  mercury. 
As  the  air  expands  it  passes  out  through  this  tube  and  escapes 
through  the  mercury  but  the  air  and  carbon  dioxide  from  out- 
side cannot  enter. 

(g)  On  a  large  leaf  of  geranium   (Pelargonium),  or  other 
plant  which  produces  starch  in  abmidance  in  its  leaves,  clamp 
on  the  upper  side  a  flat  cork  and  on  the  lower  side  a  httle  box 
(a  wooden  box  such  as  cover  glasses  come  in  will  be  satis- 
factory) blackened  inside  and  whose  sidea 

I r-T-x-r — ,  have    been    pierced  from  the  outside   by 

^^'^V'.^^^^ii'"^'^w^■■^''->|v>'^^>^.■a">  numcrous  Small  holes  running  obliquely 
away  from  the  leaf.  These  holes  admit  air 
(and  CO2)  but  as  thej^  point  awaj^  from  the 

Fig     45  — D"  ^^^^  ^^^  ^\^\^  admitted  through  them  is  ab- 

pearance  of  starch  sorbed  by  the  blackened  inner  surface  of  the 
^^'  box.    Set  the  plant  in  the  sunlight  for  sev- 

eral hours  then  remove  the  leaf  and  treat 
with  alcohol  and  iodine  as  in  (/).  The  spot  protected  from 
hght  by  the  cork  and  the  httle  box  will  show  no  starch. 
To  clamp  two  corks  together  on  both  sides  of  the  leaf  is  un- 
satisfactor}^,  as  in  that  case  not  only  is  the  light  cut  off  but  the 
CO2  as  well,  so  that  the  reason  for  the  lack  of  starch  in  that  case 
is  two  fold. 

(A)  Reserve  carbohydrate  in  the  form  of  starch  may  be 
demonstrated  in  the  tubers  of  potatoes,  root  of  sweet  potatoes 
(Ipomoea  batatas) ,  seeds  of  corn  (Zea  7/ia?/s),  wheat,  beans,  etc. 
In  the  form  of  cane  sugar  it  is  present  in  the  root  of  the  beet 
(especially  in  the  sugar  beet),  in  the  stem  of  corn  and  sugar  cane, 
etc.  As  hemicellulose  it  is  present  in  the  wood  of  mulberry 
(Morus)  and  elm  where  it  ma}'  be  demonstrated  by  treating  a 
section  with  sulphuric  acid  followed  by  iodine  solution.  Food  is 
stored  up  in  the  seeds  of  cotton,  castor  bean  (Ricinus),  flax, 
etc.,  and  in  the  scales  of  onions,  leaves  of  cabbage,  etc.,  as  fats. 


LABORATORY  STUDIES  101 

It  may  be  demonstrated  by  treating  with  dilute  osmic  acid 
solution  which  turns  fats  black,  or  withalkannin  solution,  which 
stains  the  fat  drops  red. 

(t)  Place  a  geranium  (Pelargonium)  plant  in  the  light  for 
several  hours  until  starch  has  been  produced  in  quantity  in  the 
leaves.  On  two  or  three  leaves  cut  one  or  two  of  the  main 
radial  veins  leaving  the  other  veins  intact.  Cover  the  whole 
plant  loosely  with  a  bell  jar  to  prevent  these  injured  leaves  from 
drying  out  too  much  and  place  in  the  dark  for  from  twelve  to 
twenty  hours.  Treat  these  leaves  with  alcohol  and  iodine 
solution  as  in  (/)  to  determine  the  location  of  the  starch.  It 
will  be  found  to  have  disappeared  except  from  the  portions 
bordering  on  the  cut  veins,  showing  that  it  is  through  these 
veins  (vascular  bundles)  that  the  carbohydrates  are  transported. 

(j)  Reserve  protein  in  the  form  of  aleuron  in  the  seeds  of 
beans,  peas,  etc.,  was  studied  in  connection  with  cell  inclusions 
(paragraph  24).  It  will  be  worth  while  to  repeat  these 
observations. 

(k)  Examine  one  of  the  powdery  mildews  (Erysiphaceae)  as 
an  example  of  a  hysterophytic  lower  plant  that  obtains  its 
food  from  living  plants  (i.e.  is  parasitic).  Take  a  bit  of  infected 
leaf  and  moisten  with  alcohol,  then  mount  in  water  or  dilute 
potassium  hj-drate  solution  wdth  the  infected  side  uppermost. 
By  careful  focusing  the  filaments  of  the  fungus  may  be  dis- 
tinguished and  here  and  there  may  be  seen  the  haustoria 
("suckers")  which  are  sent  into  the  epidermal  cells  of  the 
leaf.  Better  developed  haustoiia  can  sometimes  be  found  on 
making  cross-sections  of  leaves  or  stems  affected  by  downy 
mildew  (Peronosporaceae)  or  wliite  rust  (Albugo).  In  these 
cases  the  whole  fungus  except  certain  reproductive  ])arts  is 
within  the  host  plant,  growing  interccllularly  and  sending  well 
developed  haustoria  into  the  cells  between  which  it  passes. 
In  both  cases  note  the  lack  of  chlorophyll  in  the  fungus. 

(/)  Examine  a  dodder  plant  (Cuscuta)  as  an  example  of  a 
higher  plant  that  is  parasitic.  No  leaves  are  to  be  found  and 
in  most  cases  no  chlorophyll,  and  the  plant  carries  on  no 
photosynthesis.  The  original  root  which  penetrated  the  soil 
dies  as  soon  as  the  plant  has  attached  itself  to  its  host  or  even 
before.  Note  the  roots  by  which  it  obtains  its  food  from  the 
host.  Sections  of  the  stem  will  reveal  vascular  bundles,  epi- 
dermis, etc.,  but  usually  no  chlorophyll-bearing  cells. 


102  PLANT  PHYSIOLOGY 

(m)  Place  a  number  of  fresh  leaves  or  a  short  shoot  with 
leaves  in  the  large  end  of  a  retort  with  a  little  water  and  place 
the  small  end  under  a  surface  of  mercury  to  prevent  the 
entrance  of  gases.  Keep  in  a  dark  moderately  warm  place  for 
from  twelve  to  twenty-four  hours.  Note  tiiat  the  volume  of 
the  gas  does  not  seem  to  be  changed.  Carefully  without  allow- 
ing any  air  to  enter  run  a  pipette  full  of  strong  KOH  solution 
into  the  small  end  of  the  retort  or  introduce  a  small  piece  of 
stick  potash  (KOH)  with  a  few  drops  of  water,  these  rising  to 
the  surface  of  the  mercur}'.  As  the  CO2  is  absorbed  the 
mercury  rises.  When  the  ascent  ceases  (i.e.  all  the  CO2  has 
been  absorbed)  introduce  a  strong  solution  of  pyrogallic  acid. 
This  has  the  property  when  mixed  with  alkaline  solutions  of 
absorbing  oxygen.  Note  w^hether  the  mercury  rises  any 
further.  If  it  does  so  it  shows  that  some  oxygen  was  present. 
Repeat  the  experiment  using  a  retort  without  any  leaves  in  it. 
It  will  be  found  that  about  as  much  COowas  produced  by  the 
leaves  (as  shown  by  the  height  to  which  mercury  rose  with  the 
KOH  alone)  as  oxygen  was  present  (as  shown  in  the  control 
experiment  by  the  distance  the  mercury  rose  with  the  KOH 
and  pyrogallic  acid).  If  this  can  be  done  with  graduated  cylin- 
ders the  amounts  can  be  measured  more  accurately. 

(n)  That  CO 2  is  given  off  by  a  hving  plant  may  be  demon- 
strated in  the  following  waj^  also.  Place  a  potted  plant  under 
a  bell  jar  with  a  dish  of  Ba(0H)2  solution  or  (less  preferably) 
Ca(0H)2  solution.  Put  in  a  dark  place.  The  CO2  given  off 
forms  a  crust  of  BaCOc  (or  CaCOs)  on  the  surface  of  the  liquid 
while  in  a  control  experiment  with  no  plant  under  the  bell  jar 
the  amount  of  CO 2  in  the  air  (3  parts  in  10,000)  produces  only 
a  very  small  precipitate. 

(0)  Soak  some  peas  over  night  and  then  place  them  in  a 
tall  glass  jar  filling  it  about  half  full,  and  cover  with  a  vase- 
lined  glass  plate.  After  a  few  hours  remove  the  plate  and 
lower  a  burning  taper  into  the  cyHnder.  It  is  extinguished 
by  the  CO2  which  has  replaced  the  oxygen.  If  the  air  is 
very  still  it  is  more  striking  to  place  a  small  lighted  taper  in 
the  bottom  of  anotherjar  and  topour  the  CO2  from  the  jar  of 
peas  into  this  jar,  extinguishing  the  light. 

ip)  vSoak  some  peas  over  night.  Fill  a  test  tube  with  mer- 
cury and  invert  over  a  dish  of  mercury.  Force  three  or  four 
peas  under  the  mercury  so  that  they  come  under  the  edge  of  the 


LABOUATORY  STUDIES  103 

test  tube,  when  the}-  will  rise  to  its  closed  end.  Respiration 
in  its  first  (anaerobic)  stage  will  go  on  and  gas  will 
be  formed,  oftentimes  driving  nearly  all  the  mercur}^  | 
out  of  the  tube.  Introduce  a  strong  KOH  solution  L 
or  a  piece  of  stick  KOFI  and  a  little  water  under  Hffl 
the  edge  of  the  test  tube  and  the  gas  will  all  be  I^uts- 
absorbed,    showing   that  it  is  CO2  that  was  produced,  pirution 

,  GXpG  r  1- 

(q)  Yeast  plants  ordinaril}^  carrj'  on  only  this  first  ment 
stage  of  respiration  (called  fermentation  in  this  case).  ^  ^' 
To  potato  water  (made  by  grating  up  a  potato  and  boiling  it  in 
a  little  water  and  expressing  the  latter)  add  about  5  per  cent, 
glucose.  Place  in  a  flask  with  a  cork  and  a  glass  tube  bent  so  as 
to  lead  the  gas  produced  under  water.  Break  up  part  of  a  cake 
of  compressed  yeast  in  a  little  water  and  add  it  to  tlie  solution  in 
the  flask  and  insert  the  cork  and  glass  tube.  In  a  short  time 
gas  will  begin  to  escape  in  bubbles  from  the  end  of  the  tube. 
Collect  some  in  a  test  tube  and  test  in  various  ways  such  as  for 
inflammabiUtj^,  absorption  by  KOH,  etc.  It  will  be  found  to 
be  CO2.  Note  what  large  amounts  are  produced.  After  the 
evolution  of  gas  has  ceased  the  proper  chemical  tests  will  show 
the  presence  of  alcohol  in  the  liquid.  Distill  the  latter  and 
collect  the  first  part  that  comes  over.  Add  to  it  some  strong 
KOH  solution  and  some  flakes  of  iodine,  and  heat.  If  alcohol  is 
present  a  strong  odor  of  iodoform  will  be  produced  and  if  much 
is  present  this  will  show  as  a  yellow  precipitate. 

(r)  The  liberation  of  heat  during  resj^iration  can  be  demon- 
strated by  placing  a  quantity  of  soaked  peas  or  a  number  of 
mushrooms  just  expanding  in  a  flask  with  an  accurate  chemical 
thermometer  bulb  in  their  midst  and  placing  this  flask  in  a 
mass  of  cotton  in  another  vessel  and  covering  all  with  several 
layers  of  cloth,  leaving  only  the  thermometer  tube  exposed. 
Often  the  temperature  within  tlie  flask  will  rise  3  or  4  degrees 
or  more  above  that  of  the  surrounding  air.  Of  course  this 
experiment  must  be  carried  on  in  a  room  where  the  temperature 
is  fairly  constant.  If  a  Dewar  bulb  or  a  Thermos  bottle  is  used, 
these  being  double  walled  with  a  vacuum  between  so  that  the 
loss  of  heat  is  very  small,  the  difference  of  temperature  is 
much  more  marked. 

(.s)  Without  special  thermostats  where  temperatures  can  be 
controlled  exactly,  satisfactory  ex])eriments  as  to  the  cardinal 
points  of  temperature  cannot  be  made.     However,  it  will  be 


104  PLANT  PHYSIOLOGY 

helpful  in  the  autumn  to  list  the  plants  most  susceptible  to 
injury  and  those  that  suffer  least  from  frost. 

147.  Growth.  In  the  one-celled  plants,  or  plants 
made  up  of  undifferentiated  cells,  growth  is  a  function  of 
every  cell.  It  enlarges  up  to  a  certain  point  and  then 
divides  into  two  cells  which  enlarge  and  divide,  etc. 
In  some  cases  the  cell  divides  internally  into  many  small 
cells  which  enlarge  until  they  reach  the  size  of  the  parent 
cell  and  repeat  the  process.  The  growth  of  a  cell  in- 
volves a  number  of  factors.  Among  these  are  the  in- 
crease in  the  amount  of  cytoplasm  and  sometimes  a  great 
increase  in  the  amount  of  cell  sap,  also  the  enlargement 
of  the  cell  wall  in  area  and  frequently  also  in  thickness. 
These  cells  are  meristematic  in  many  features.  In  such 
plants  we  can  hardly  dissociate  growth  from  reproduction. 

148.  In  the  more  complex  plants  we  find  some  parts 
that  are  the  seat  of  the  growth,  the  growing  points  and 
adjacent  region  and  cambium  layers,  while  the  rest  of  the 
plant  practically  ceases  to  grow.  The  reproductive 
functions  are  carried  on  by  special  parts  of  the  plant 
which  have  nothing  to  do  with  its  ordinary  growth. 
The  growth  in  such  plants  takes  place  still  by  the 
process  of  cell  growth  and  division,  but  we  find  that  these 
differ  considerably  from  the  case  in  one-celled  plants. 
Thus  near  the  tips  of  the  growing  points  the  cells  in- 
crease their  cytoplasm  and  cell  wall  area  so  as  to  become 
perhaps  twice  as  large,  and  then  divide  and  form  new  cells 
as  is  the  case  in  one-celled  plants  except  that  the  cells 
remain  attached.  Gradually,  however,  some  of  these 
cells  that  by  the  formation  of  new  cells  have  come  to  lie 
further  from  the  tip  increase  more  and  more  in  size 
and  are  not  so  active  in  their  division.  This  increase  in 
size  takes  place  largely  by  an  increase  in  size  of  the 
vacuoles  so  that  the  cells  contain  proportionally  less  and 
less  cytoplasm,  although  probably  the  amount  of  cyto- 


GROWTH  105 

plasm  actually  docs  increase,  or  decreases  but  little.  In 
other  words  the  growth  of  the  cell  is  mainly  accomplished 
by  absorbing  large  amounts  of  water,  the  cell  wall  being 
increased  in  area  so  as  to  keep  pace  with  the  increase  in 
volume.  It  is  possible  that  in  some  cases  where  the 
growth  of  the  cell  is  very  rapid  the  total  amount  of  cyto- 
plasm in  the  cell  may  actually  be  reduced  in  manu- 
facturing the  additional  cell  wall  substance  required. 
In  this  growth  we  can  distinguish  three  phases  which  can 
be  more  or  less  clearly  set  off,  viz.,  formative  phase,  phase 
of  enlargement  and  phase  of  differentiation  or  maturation. 

149.  Thus  it  comes  about  that  at  the  growing  root  tip 
or  tip  of  the  stem  we  can  distinguish  an  area  near  to  the 
tip  where  growth  is  not  very  rapid  but  cell  division  is 
taking  place  abundantly  (i.e.  the  cells  are  in  the  formative 
phase  of  growth),  and  another  area  into  which  the  first 
grades,  and  a  little  distance  back  from  it,  where  the  cells 
are  enlarging  very  rapidly  and  but  little  cell  division  is 
taking  place  (i.e.  the  cells  are  in  the  phase  of  enlarge- 
ment). This  gradually  grades  off  into  that  portion  of 
the  root  or  stem  where  growth  in  size. is  no  longer  oc- 
curring but  where  the  various  tissue  differentiations  are 
taking  place  (i.e.  the  phase  of  differentiation).  In  the 
root  these  zones  are  well  marked,  while  in  the  stem  the 
elongation  may  persist  for  a  long  while  and  may  become 
localized  in  nodes  while  the  internodes  cease  to  grow. 
In  this  case  the  nodes  usually  retain  some  meristem  and 
possess  the  power  of  producing  new  cells  as  well  as  in- 
creasing in  size. 

150.  There  are  several  factors  that  influence  plant 
growth.  There  must  in  the  first  place  be  sufficient  food 
stuffs  to  enal)le  the  cells  to  manufacture  the  necessary 
new  cytoplasm  and  cell  wall.  Then  there  must  be 
sufficient    organic    substances  to  produce   the   osmotic 


106  PLANT  PHYSIOLOGY 

pressure  necessary  to  take  in  the  requisite  large  quanti- 
ties of  water  that  increase  the  bulk  of  the  cell  so  greatly 
during  the  phase  of  enlargement.  Then  sufficient  food 
substances  must  also  be  present  to  supply  in  the  process 
of  respiration  the  energy  necessary  for  growth.  Further- 
more the  water  supply  must  be  ample,  for  growth  ceases 
immediately  if  the  cells  of  the  plant  are  not  kept  strongly 
turgid,  hence  the  reason  that  in  a  dr}^  season  a  plant  may 
remain  alive  for  months  on  a  minimum  of  water,  but 
scared}^  grow  at  all.  The  temperature  also  has  a 
marked  influence  on  growth.  The  cardinal  points  of 
temperature  for  growth  are  often  quite  different  from 
those  for  photosjmthesis  or  respiration  in  the  same  plant. 
In  some  plants  that  come  up  through  the  snow  the 
optimum  temperature  for  growth  may  be  but  little 
above  0°  C,  while  in  Indian  corn,  for  example,  the  opti- 
mum lies  between  37°  and  42°  C. 

151.  The  effect  of  light  upon  grow^th  is  noteworthy. 
Careful  records  of  the  rate  of  growth  with  automatically 
recording  instruments  show  that,  given  constant  tem- 
perature, the  growth  is  much  more  rapid  in  darkness 
than  in  light.  If  the  rays  from  the  blue  end  of  the 
spectrum  are  excluded  growth  is  scarcely  if  at  all  checked 
by  light.  The  absence  of  light,  however,  although  favor- 
ing the  elongation  of  the  plant,  prevents  the  normal  form- 
ation of  leaves.  This  is  possibly  due  in  part  to  lack  of 
food,  but  it  seems  probable  that  a  definite  stimulus  on  the 
part  of  light  is  needed  before  leaves  will  be  produced  in 
the  normal  form  and  size.  Plants  kept  in  the  dark  become 
much  elongated  (remaining  pale  in  color)  with  only  rudi- 
ments of  leaves.  Such  plants  are  said  to  be  etiolated. 
To  a  certain  degree  this  is  useful  to  a  plant  in  that  a  tuber 
or  seed  buried  too  deep  produces  an  abnormally  elongated 
shoot  which  may  thus  be  able  to  reach  the  light. 


CIROWTH  107 

152.  The  amount  of  growth  in  a  given  length  of  time 
varies  with  the  plant.  Sonic  trees  in  dry  regions,  e.g. 
Ccrcocarpus  parvifolius,  the  mountain  mahogany  of 
Colorado,  may  scarcely  attain  a  height  of  two  meters  in 
one  hundred  j-ears,  while  a  morning  glory  vine  (Ipomoea) 
may  grow  17  cm.  per  day,  a  bamboo  shoot  60  cm.  per 
day  and  a  stamen  of  Avheat  1.8  mm.  per  minute,  i.e.  at  a 
rate  of  over  25  meters  a  day  (but  of  course  this  rate  of 
growth  actually  lasts  only  a  few  minutes). 

153.  As  growth  occurs  in  a  stem  or  root  various 
tensions  arise  owing  to  the  unequal  amount  of  growth  in 
different  parts.  Thus  the  pith  of  many  plants  (especially 
herbaceous  ones)  elongates  considerabl}"  when  removed 
from  the  stem  and  the  surrounding  portions  shorten  a 
little.  While  they  remain  in  the  plant  the  result  is  that 
certain  parts  of  the  plant  are  stretched  and  the  pith 
compressed,  w^hich  stiffens  the  plant  just  as  in  a  turgid  cell 
the  stretched  cell  wall  pressing  against  the  osmotic 
pressure  within  the  cell  renders  the  cell  stiff.  Bark  of 
trees  usually  shows  a  circumferential  stretching  also 
which  helps  to  keep  the  stem  rigid. 

Laboratory  Studies,  (a)  Examine  plants  of  Protococciis 
(one to  few  celled)  or  of  Spirogyra  (chain  of  cells).  Cells  of 
different  sizes  will  be  found  but  the  largest  cells  are 
rarely  more  than  twice  as  large  as  the  smallest  ones. 
Here  each  cell  grows  and  divides  for  itself  and  in  the 
case  of  the  first  the  cells  soon  separate,  forming  new 
plants. 

(6)  Take  a  germinated  seed  of  Indian  corn,  sun- 
flower or  other  plant  and  on  a  rapidly  growing  root, 
using  a  thread  dipped  in  India  ink,  mark  lines  1  mm. 
apart  making  the  first  mark  1  mm.  back  from  the  tij) 
(special  markers  for  this  i)urpose  may  be  bought,  but 
although  more  convenient  are  not  indispensible).  Place  fu..  47. 
this  seed  on  moist  cotton  with  the  marked  root  J~r^J,"„*i5i' 
directed  downward  and  cover  with  a  bell  jar  to  cxpcri- 
prevent  drying  out.     Examine  at  intervals  of  several 


108  PLANT  PHYSIOLOGY 

hours  to  determine  in  what  segment  so  marked  the  most 
rapid  growth  occurs.  It  must  be  remembered  that  tliis  zone 
of  most  rapid  growth  is  rapidlj^  passing  down  the  root  all 
the  time,  keeping  about  the  same  distance  back  from  the  root 
tip,  so  that  the  marked  root  must  not  be  left  too  long  before 
examination  or  the  conclusions  will  be  faulty. 

(c)  Attach  the  thread  of  an  auxanometcr  (instrument  for 
measuring  growth)  to  the  tip  of  a  leaf  just  growing  out  of  an 
onion  or  hj-acinth  bulb  or  to  the  tip  of  the  flower  scape  of  such 
a  plant,  or  just  below  the  cotyledons  of  a  sunflower  seedHng. 

If  possible  have  the  plant  in  a  situation  where 
it  is  almost  equally  lighted  from  all  directions. 
If  the   instrument  is  not  self-recording  readings 
should  be  made  every  one  or  two  hours  during 
the  day  and  night.    If  the  records  are  automat- 
ically made  the  readings  need  not  be  taken  during 
the  course  of  the  experiment  but  the  records  can 
be  studied  afterward.    So  far  as  possible  keep  the 
nomete/Sr*  temperature  constant.    Interesting  results  may 
be  obtained  by  varying  the  temperature  while 
keeping  the   intensity   of   the  light  the  same  or  bj^  varjdng 
the  hght  with  constant  temperature.    The  effect  of  keeping 
the  soil  very  wet  and  very  dry  may  also  be  compared. 

(d)  Observe  a  potato  that  has  started  to  grow  in  a  dark 
corner  of  a  cellar  and  compare  its  growth  with  that  from  a  tuber 
that  has  been  grown  in  full  hght. 

(e)  Place  potted  plants  under  bell  jars  as  follows:  (1)  clear 
white  glass,  (2)  double  bell  jar  with  space  filled  with  saturated 
K2Cr207  solution,  (3)  double  jar  with  space  filled  with  saturated 
cuprammonia  solution.  Compare  the  growth.  Note  also  the 
differences  in  the  color  and  development  of  the  leaves.  The 
cuprammonia  solution  is  prepared  by  carefully  adding  to  a 
copper  sulphate  solution  sufficient  ammonia  to  precipitate  all  of 
the  copper  as  copper  hydroxide  but  not  adding  enough  ammonia 
to  redissolve  the  precipitate.  Filter  and  wash  the  precipitate 
and  then  dissolve  it  in  strong  ammonia  using  only  enough  of 
the  latter  to  completely  dissolve  it.  This  must  not  be  done 
on  the  filter  paper  as  the  solution  thus  formed  dissolves  cellulose. 

(/)  The  rate  of  growth  under  normal  conditions  can  be  meas- 
ured by  an  auxanometer  or  with  a  horizontal  microscope  or  in 
the  case  of  rapidly  growing  plants,  such  as  Indian  corn,  morn- 


REPRODUCTION  109 

ing  glory  vine,  bamboo,  etc.,  it  can  be  measured  even^  day  with 
a  ruler.  ]\Iake  and  record  such  measurements  night  and  morn- 
ing for  several  kinds  of  plants. 

154.  Reproduction.  This  is  the  ultimate  function  of 
all  plants.  For  many  it  is  the  final  function  of  hfe,  the 
death  of  the  old  individual  occurring  with  the  formation 
of  the  new  individual.  It  is  perhaps  to  be  considered  as 
the  final  act  of  growth  toward  which  all  development 
of  the  plant  has  been  leading. 

155.  In  many  of  the  lower  plants,  especially  those 
that  are  undifferentiated,  reproduction  is  nothing  more 
than  cell  division  followed  by  separation  of  the  cells  thus 
produced.  In  the  more  differentiated  plants,  however, 
we  find  certain  cells  set  aside  for  reproductive  purposes. 
These  may  be  at  first  ordinary  vegetative  "cells  that 
later  take  up  the  reproductive  function,  or  they  may  be 
destined  for  the  latter  from  their  beginning. 

156.  Very  early  in  the  vegetable  and  animal  kingdoms 
two  types  of  reproduction  become  recognizable,  the 
asexual  and  the  sexual.  The  former  consists  essentially 
of  the  division  of  the  plant,  or  of  the  separation  from  it 
of  single  cells  or  groups  of  cells  or  even  whole  plant 
members.  By  further  growth  these  parts  thus  pro- 
duced become  like  the  parent  plant.  Not  to  be  confused 
with  true  asexual  reproduction,  is  the  development 
of  the  gametophyte  from  the  spores  produced  by  the 
sporophyte. 

157.  Sexual  reproduction  is  fundamentally  different 
from  asexual  reproduction  in  that  there  is  requisite  the 
union  of  two  distinct  cells  (or  at  least  their  nuclei)  to 
form  a  single  cell,  the  zygote.  This  may  develop 
directly  into  a  new  plant  or  into  a  mass  of  cells  (the 
spore  fruit),  which  produces  onlj^  eventually  the  repro- 
ductive cells,  which  give  rise  to  the  new  plants.     The 


no  PLANT  PHYSIOLOGY 

uniting  cells  (gametes)  may  come  from  the  same  or 
from  different  plants,  indeed  they  may  be  sister  cells, 
i.e.  formed  by  the  division  of  one  cell,  but  this  is  not 
common.  They  may  be  alike  (isogamous)  or  unlike 
(heterogamous). 

158.  As  we  proceed  from  the  simple  to  more  complex 
plants  in  the  study  of  sexual  reproduction  we  find  entering 
in,  the  principle  of  "increased  parental  care."  In  the 
lowest  plants  with  sexual  reproduction  the  gametes 
unite  outside  of  the  parent  plant,  at  a  higher  stage  one 
gamete  (the  egg)  is  retained  in  the  parent  plant  and  is 
fertilized  by  the  motile  sperm.  Still  higher  the  egg  is 
surrounded  by  special  protective  structures  (cystocarp, 
archegone,  etc.)  and  produces  no  longer  a  simple  zygote 
but  a  spore  fruit  w^hich  may  also  be  included  in  the  pro- 
tective envelope.  A  still  higher  stage  is  whei'e  the 
spore  fruit  is  so  highly  differentiated  that  it  becomes  a 
separate  generation  (sporophyte),  capable  of  separate 
existence,  similar  to  or  differing  in  appearance  from  the 
parent  generation  (gametophyte).  Highest  of  all  we 
find  the  sporophyte  becoming  the  prevalent  generation, 
the  gametophyte  being  retained  within  its  protective 
tissues  and  only  developing  far  enough  to  permit  sexual 
reproduction  to  occur. 

159.  Each  gamete  of  the  same  species  has  the  same 
number  of  chromosomes  in  its  nucleus.  The  cell  re- 
sulting from  their  union,  the  zygote,  has  double  this 
number  (diploid  number).  Where  a  zygote  is  formed 
which  gives  rise  directly  to  a  plant  like  the  original  one, 
the  reduction  in  the  number  of  the  chromosomes  from 
the  diploid  to  the  haploid  number  (see  paragraphs  35 
and  160),  occurs  with  the  germination  of  the  zygote. 
Where  a  spore  fruit  or  sporophytic  generation  occurs  its 
cells  retain  the  diploid  number  and  the  reduction  divi- 


REDUCTION  OF  CHROMOSOMES 


111 


sion  does  not  enter  in  until  tlie  spores  are  being  produced, 
which  give  rise  to  the  sexual  generation  (gametophyte). 
This  latter  has  the  haploid  number  of  chromosomes  in 
its  nuclei.  We  must  thus  distinguish  carefully  between 
typical  asexual  reproduction,  where  the  resulting  plant 
is,  as  it  were,  but  a  separated  part  of  the  mother  plant, 
and  the  formation  of  a  gametophytic  generation  from 
the  spore  produced  in  the  sporophytic  generation.  In- 
deed each  of  these  generations  may  have  typical  asexuiil 
reproduction  leading  simply  to  the  formation  of  other 
plants  of  the  same  generation. 

160.  After  the  union  of  gametes  the  chromosomes 
from  the  two  gametes  remain  separate,  but  usually  the 
corresponding  chromosomes  from  each  gamete  lie  close 
together.  In  the  reduction  division  the  chromosomes 
gather  at  the  equator  of  the  spindle  as  double  chromo- 
somes, in  all  probability  representing  the  two  corre- 
sponding chromosomes  from  the  two  gametes.  Before 
this  stage  is  reached,  and  while  the  chromatin  matter 
is  found  on  fine 
threads,  there  is  a 
characteristic  bunch- 
ing together  of  these 
threads  (called  the 
synapsis)  in  the  course 
of  which  it  is  sup- 
posed that  certain 
characters  become  ex- 
changed in  the  corres- 
ponding  c  h  r  o  m  o  - 
somes.  These  double  chromosomes  split  apart  and  as 
single  ones  go  to  the  opposite  poles.  There  are  thus 
entering  into  each  daughter  nucleus  only  as  many  chromo- 
somes as  were  originally  present  in  the  gametes.     These 


Fig.  49. — Reduction  division  (diagrammatic). 


112  PLANT  PHYSIOLOGY 

chromosomes  do  not,  however,  correspond  exactly  to  the 
originals,  for  in  the  synaptic  stage  there  has  been  an 
exchange  of  some  characters.  At  the  next  division  the 
nuclear  phenomena  are  like  those  of  the  ordinary 
vegetative  division. 

161.  These  peculiarities  of  haploid  and  diploid  chro- 
mosome number,  reduction  division,  and  ordinary  (so- 
matic) division  of  the  nuclei,  as  well  as  other  observed 
phenomena  of  heredity,  have  led  most  investigators  to 
conclude  that  the  chromosomes  are  the  chief  bearers  of 
heredity.  In  sexual  reproduction,  then,  is  found  a  means 
of  combining  in  the  most  complicated  ways  the  minute 
or  larger  differences  found  in  the  different  parents. 

162.  Variations.  Hardly  any  two  plants  are  exactly 
alike.  The  differences  are  of  two  kinds:  (1)  a  response 
of  the  plant  to  slightly  or  greatly  different  environ- 
mental conditions,  and  (2)  a  difference  in  the  constitu- 
tions of  the  plants  that  leads  them  to  respond  somewhat 
differently  in  morphological  or  physiological  characters 
when  exposed  to  the  same  conditions.  These  latter 
are  the  only  ones  that  demand  attention  here.  They 
may  be  slight  differences  that  are  apparently  not  inherit- 
able (i.e.  although  the  somatic  or  vegetative  cells  are 
somewhat  different  the  sexual  cells  are  not  so),  or  there 
may  actually  have  taken  place  a  change  in  the  constitu- 
tion of  the  protoplasm  that  affects  also  the  reproductive 
cells,  so  that  the  heredity  carriers  (probably  the  chromo- 
somes) are  slightly  different  in  the  different  plants. 

163.  Gregor  Mendel,  in  18G6,  published  a  paper  in 
which  he  pointed  out  that  certain  characters  that  differed 
in  the  two  parents  and  that  are  mutually  exclusive 
(i.e.  that  allow  of  no  intermediate  form)  would  appear  in 
the  second  generation  in  a  pure  form  in  some  of  the 
plants.     This  is  now  explained  by  the  phenomena  taking 


VARIATIONS  113 

place  in  connection  with  the  reduction  division,  where 
during  synapsis  certain  character-determining  units  in 
the  chromosomes  may  become  exchanged,  so  that  the 
chances  are  about  equal  whether  one  or  the  other  char- 
acter from  respectively  one  or  the  other  parent  will  be 
present  in  the  new  cell.  Mendel  found  that  about  one- 
fourth  of  the  second  generation  plants  show  a  given  char- 
acter from  one  of  the  original  plants  and  one-fourth  the 
character  from  the  other  plant,  while  one-half  still  re- 
tains (at  least  potentially)  both  characters,  although  only 
one  is  visible,  it  being  ''dominant"  over  the  other  char- 
acter which  is  ''recessive.'^  That  both  characters  are 
present  is  shown  by  the  fact  that  seeds  from  this  half 
produce  plants  which  divide  up  again  into  one-fourth, 
one-fourth,  and  one-half,  etc. 

164.  In  sexual  reproduction  the  various  differences 
borne  by  the  different  chromosomes,  or  perhaps  more 
accurately  by  the  unit  structures  of  the  chromosomes, 
will  be  redistributed  among  the  daughter  and  grand- 
daughter plants  in  new  combinations.  Some  of  these 
will  be  advantageous  to  the  plant,  and  it  will  succeed 
better  and  be  able  to  reproduce  more  freely;  other  com- 
binations may  be  less  favorable,  and  the  plants  with 
such  combinations  will  have  a  poorer  chance  in  the 
struggle  for  existence,  and  will  not  reproduce  so  freely. 
As  a  result,  ''Natural  Selection'^  sorts  out  those  whose 
combinations  are  most  favorable.  Thus  we  see  that 
sexual  reproduction  forms  a  means  by  which  the  con- 
stantly arising  individual  differences  (and  why  they  arise 
we  do  not  know)  are  made  use  of  in  the  most  manifold 
combinations,  the  most  favorable  of  which  are  perpet- 
uated. This  is  what  was  called  by  Darwin  "The 
survival  of  the  fittest." 

165.  These    inheritable    variations  may  be  slight  or 


lU  PLANT  PHYSIOLOGY 

they  may  be  strongly  marked.  They  are  often  called 
"mutations"  to  distmguish  them  from  the  non-in- 
heritable variations.  If  the  plants  showing  them  are 
considerably  better  able  to  exist,  they  will  rapidly  crowd 
out  the  less  favorably  constituted  plants,  and  thus  a 
new  species  will  replace  the  old.  Under  other  environ- 
mental conditions  this  new  feature  may  be  less  favorable 
and  so  the  older  form  will  persist.  Thus  we  find  plants 
with  all  sorts  of  differences  or  what  we  call  ''species," 
all  over  the  world.  Some  plants  have  changed  but  little 
apparently  from  their  primitive  structure,  as  they  were 
able  to  persist  in  that  form  under  certain  conditions, 
while  some  of  their  descendants,  it  may  be,  have  pro- 
gressed far  along  the  evolutionary  line.  Thus  we  find 
the  Vegetable  Kingdom  made  up  not  only  of  the  ends  of 
long  evolutionary  branches  but  also  of  stragglers  that 
have  progressed  only  a  very  little  way,  and  of  those  that 
have  grown  further  before  branching  out  in  some  other 
direction.  It  is  this  fact  that  enables  us  to  attempt  to 
show  the  probable  course  of  evolution  (phylogeny)  of  the 
Vegetable  Kingdom  in  our  arrangement  of  the  plants  now 
existing. 

166.  The  conditions  that  favor  reproduction  have 
been  worked  out  for  a  good  many  plants,  but  are  un- 
known for  the  vast  majority.  It  seems  that  those  con- 
ditions that  favor  continued  vegetative  growth,  such  as 
an  abundance  of  water  and  all  foods,  tend  to  delay  or 
prevent  reproduction.  On  the  other  hand,  there  must 
usually  be  a  certain  amount  of  food  stuffs  stored  up. 
If  these  can  be  prevented  from  accumulating,  or  can  be 
used  up  by  promoting  vegetative  growth,  reproduction 
will  be  held  back.  In  many  cases,  however,  the  repro- 
ductive stage  comes  on  in  spite  of  all  efforts  to  keep  it 
back,  showing  that  not  all  the  factors  are  known. 


PLANT  BREEDING  115 

167.  The  breeding  of  plants  is  an  application  of  the 
principles  of  reproduction  and  heredity  to  the  production 
of  plants  with  certain  desirable  characteristics.  In- 
stead of  waiting  for  the  chance  production  of  a  desirable 
type  of  plant,  the  plant  breeder  either  grows  many  plants 
in  conditions  under  his  control  and  selects  for  further 
propagation  those  he  deems  most  desirable  (method  of 
selection),  or  he  takes  two  distinct  plants,  each  with 
certain  characters  that  he  desires,  and  crosses  them,  and 
grows  the  progeny  in  large  numbers  for  several  generations 
until  by  the  laws  of  chance  in  the  distribution  of  the 
unit  character  determinants  there  appears  a  plant 
combining  the  desirable  characters  of  the  two  parents. 
This  is  the  method  of  hybridization  or  crossing.  The 
discovery  by  Mendel  of  the  segregation  of  characters  by 
definite  laws  of  numbers  (see  paragraph  165)  has  given  a 
great  impetus  to  this  line  of  work. 

Laboratory  Studies.  Not  much  can  be  done  in  the  way  of 
laboratory  work  on  this  subject.  In  the  study  of  the  different 
forms  of  plants  in  the  later  chapters  of  the  book,  the  points 
emphasized  in  the  foregoing  paragraphs  should  be  borne  in 
mind.  A  few  suggestions  are  made  for  observations  on  the 
part  of  the  student. 

(a)  Find  and  compare  carefully  a  dozen  different  plants  of 
timothy  {Phleinn  prateiisc),  red  clover  {Trijolmm  pratense), 
ribbed  plantain  (Plantogo  lanccoJata),  etc.  Select  those 
plants  of  the  same  age  and  from  as  ncarlj^  as  possible  the  same 
soil  and  growing  under  the  same  environmental  conditions. 
Note  how  thc}^  differ  in  height ;  number,  size  and  sluii)e  of  leaves; 
size  of  flower  heads;  number  of  flowers  in  the  head;  amount  of 
hairiness  of  various  parts,  etc. 

(6)  Compare  plants  of  the  same  kind  grown  in  sun  and  shade, 
in  dry  and  moist  soils,  in  barren  and  on  fertile  ground,  for 
differences  due  largely  to  the  environment.  Note  the  (Hffcr- 
enccs  in  the  times  of  flowering  and  of  ripening  of  seeds,  as  well 
as  the  structural  differences. 


116  PLANT  PHYSIOLOGY 

168.  Movements.  Plant  movements  are  of  four 
kinds:  (1)  hygroscopic,  (2)  protoplasmic,  (3)  turgor^ 
and  (4)  growth  movements.  The  first  is  a  strictly 
physical  phenomenon  of  dead  cells,  the  last  three  are 
functions  of  living  cells  or  tissues. 

169.  Hygroscopic  Movements.  Cell  walls  have  a 
great  power  of  iml^ibition  of  water,  and  when  filled  with 
water  have  a  greater  volume  than  when  dry.  In  many 
plant  organs  certain  cell  walls  have  a  greater  power  of 
imbibition  than  others,  or  in  some  cases  certain  tissues 
on  one  side  prevent  the  organs  from  elongating  or  con- 
tracting on  that  side.  The  result  in  either  case  is  that 
as  the  cell  walls  absorb  water  or  give  it  up  a  curvature 
takes  place.  This  may  be  a  simple  bending  or  may  consist 
of  twisting.  Mostly  the  organs  straighten  out  on  becom- 
ing wet  and  curve  or  twist  as  they  dry.  In  some  cases  the 
differences  in  the  moisture  content  of  the  air  are  sufficient 
to  produce  movements.  These  movements  are  of  value  to 
the  plant  in  opening  reproductive  organs  (sporangia,  seed 
capsules,  etc.)  or  in  enabling  seeds  to  penetrate  the  ground 
(twisting  of  the  long  awn  of  porcupine  grass,  Stipa). 

170.  In  the  case  of  the  sporangia  of  the  common  ferns 
(Potypodiaceae),  the  cell  lumen  as  well  as  the  walls  is 
filled  with  water.     As  the  water  evaporates  through  the 

cell    wall,    the    cell 


Ob,     O, 


-     o^ 


'^^^  <> 


contracts  to  compen- 
?=?^^I'VOo  sate  for  the  water 
lost.  As  the  walls 
are  thin  and  collap- 
sible   on     one    side 

Fig.  50.-Dispcrsal  of  fern  spores.  Ouly,    and  thick    but 

flexible  on  the 
others,  the  cell  contracts  more  and  more  toward  the  thin 
side  until  the  row  of  cells  instead   of  being  in  a  nearly 


PROTOPLAS]\IIC  MOVEMENTS  117 

complete  circle  with  the  thin  wall  at  the  outside,  is  bent 
back  into  almost  a  reverse  circle,  the  whole  row  being  now 
under  high  tension.  As  the  evaporation  proceeds,  further 
contraction  becomes  impossible,  and  the  collapsed  thin 
cell  walls  become  dry  in  spots.  These  dry  spots  are  per- 
meable to  air,  which  rushes  into  them  and  permits  the 
whole  ring  to  snap  back  with  extraordinary  violence, 
flinging  the  spores  a  comparatively  long  distance. 

171.  Protoplasmic  Movements.  We  may  distinguish 
two  types  of  these,  the  movements  of  the  cytoplasm 
within  the  cell  and  the  movement  of  the  cell  as  a  whole, 
due  to  the  motion  of  the  cytoplasm  or  special  parts  of  it 
(cilia  or  flagella). 

172.  The  motion  of  cytoplasm  within  the  cell  seems 
to  be  a  normal  phenomenon  in  all  living  cells  whose 
protoplasm  has  imbibed  enough  water  to  make  it  rather 
liquid,  i.e.  in  all  active  cells.  It  is  probably 
entirely  absent  in  so-called  dormant  cells,  such  ^ 
as  the  cells  of  dry  seeds,  etc.  In  many  cells  it 
cannot  be  distinguished  except  by  special  methods. 
The  motion  may  consist  of  a  rotation  of  all  the 
cytoplasm  of  the  cell  except  a  thin  layer  against 
the  cell  wall  (as  in  Chara  and  Nitella),  or  of 
large  streams  in  which  chloroplasts  and  cell  inclu-  pio.  51. 
sions  are  swept  along  (as  in  Philotria),  or  in  cur-  i^nTpfo- 
rents  in  the  parietal  cytoplasm  and  delicate  (tEIS 
strands  crossing  the  vacuole  (as  in  Tradescantia) ,  *'^°***^- 
or  it  may  consist  of  rather  local  disturbances. 

173.  Of  especial  interest  are  those  movements  by 
which  the  nucleus  is  carried  from  one  part  of  the  cell  to 
the  other.  Thus  in  a  cell  that  is  growing  rapidly  on  one 
side  or  secreting  abundantly  at  one  side,  the  nucleus 
is  often  carried  to  the  point  of  activity.  The  chloroplasts, 
too,  change  their  position  with  reference  to  the  light.    If 


Q> 


118  PLANT  PHYSIOLOGY 

tlie  light  is  dim,  they  are  carried  to  the  top  or  bottom 
of  the  cell,  where  they  will  get  the  strongest  light  broad- 
side. If  the  light  is  too  strong,  they  are  carried  to  the 
sides  of  the  cell,  where  the  light  will  only  strike  them 
edgewise. 

174.  The  locomotion  of  cells  is  accomplished  mostly 
by  the  lashing  movements  of  slender  cytoplasmic  pro- 
jections from  the  surface  of  the  naked  cell.  If  few  in 
number  and  long,  they  are  usually  called  fiagella.  If 
numerous  and  rather  short,  they  are  called  cilia.  When 
single  or  few,  they  are  usually  attached  at  the  anterior 

end  of  the  cell.  A  few  plant  cells 
move  by  amoeboid  motion,  i.e. 
send  out  processes  or  lobes  into 
which  the  whole  protoplasm  flows. 
The  cells  of  diatoms  (Bacillario- 
ideae)  are  provided  with  cell  walls 
of  cellulose  so  filled  with  silica  as 

Fig.  52.— Flagellate  cells,        ,         .  ,       ,.  i      i     -,,1 

(uiothrix,  pieurociadia.      to    bc    nou-clastic    and    brittle. 

JMarchantia,    Struthiopteris,        ^  ,.     ,  ,,  ,         , 

Zainia).  lu  some  diatoms  the   protoplasm 

comes  to  the  surface  through  a 
longitudinal  slit,  the  raphe,  and  its  longitudinal  motion 
in  this  slit  is  probably  the  cause  of  the  motion  of  the  cell. 
Finally,  must  be  mentioned  the  motion  of  some  diatoms 
as  well  as  desmids,  and  some  of  the  blue-green  algae 
(e.g.  Oscillatoria)  which  is  ascribed  to  the  secretion  of  a 
slime  through  the  cell  wall.  The  bending  of  the 
Oscillatoria  filaments,  however,  may  be  due  to  proto- 
plasmic contraction. 

175.  All  of  these  movements  are  dependent  on  an  ample 
supply  of  oxygen,  and  cease  very  quickly  in  its  absence. 
The  usual  cardinal  points  of  temperature  can  be  found 
for  these  as  well  as  for  other  functions  of  the  cell.  Ap- 
parently the  movements  within  the  cell  are  of  use  in 


LOCOMOTION  OF  CELLS  110 

distributing  various  food  products  as  well  as  other  sub- 
stances throughout  the  cell. 

176.  In  motile  cells  there  is  observable  a  response 
in  direction  of  the  movements  to  various  external  stimuli. 
Thus  many  cells  swim  toward  the  light,  or  away  from  it 
(positive  and  negative  phototaxy).  Others  swim  to- 
ward or  away  from  various  chemical  substances  (e.g. 
food  matters,  acids,  etc.)  diffusing  through  the  water, 
this  being  called  chemotaxy.  In  many  cases  a  degree 
of  light  or  of  concentration  of  a  chemical  that  causes 
positive  reaction,  when  increased  beyond  a  certain  point 
repels  the  cell.  It  is  not  always  the  case  that  harmful 
chemical  substances  (poisons)  repel  the  cell,  although 
usually  this  is  the  case. 

Laboratory  Studies,  (a)  Insert  the  point  of  the  fruit  of 
porcupine  grass  (Stipa)  into  a  cork  or  fasten  the  fruit  of  cranes- 
bill  (Erodium)  to  a  cork  with  a  drop  of  seahng  wax,  with  the 
main  shaft  of  the  fruit  upright,  and  place  a  marker  opposite 
the  tip  of  the  bent  portion.  Place  a  bell  jar  partially  lined  with 
wet  filter  paper  over  it  and  note  how  it  changes  its  position  and 
the  direction  of  the  motion.  Remove  the  bell  jar  and  note  the 
change  in  the  direction  of  motion.  By  spraying  a  fine  mist  on 
the  specimen  a  lively  movement  will  be  obtained. 

(b)  Mount  several  ripe  sporangia  of  a  fern  in  a  very  little 
water  without  a  cover  glass  and  watch  the  motion  as  the  water 
dries  out. 

(c)  Examine  some  of  the  end  cells  of  Chara  or  Xitella  for 
rotatory  movement  of  cytoplasm,  the  leaf  of  Philotria  for  large 
streams  of  cytoplasm  carrying  the  chloroplasts  with  them,  the 
stamen  hairs  of  Tradescantia  or  the  stem  hairs  of  petunia, 
tomato  or  watermelon  for  more  delicate  strands  of  streaming 
cyto])Iasm. 

(d)  With  some  of  the  foregoing  test  the  effect  on  the  move- 
ment of  cold  (laying  on  a  block  of  ice)  and  heat  (up  to  40°  or 
45°  C),  examining  again  at  room  temperature. 

(e)  Place  some  green  felt  (Vauchoria)  that  has  been  growing 
on  the  surface  of  the  ground  in  a  dish  of  water.     Often  this  will 


120  PLANT  PHYSIOLOGY 

cause  it  to  form  its  multiciliate  zoospores.  Study  their  motion. 
Study  also  zoospores  of  Ulothrix,  Chaetophora  or  Draparnaldia 
which  can  often  be  obtained  by  bringing  these  algae  into  the 
laboratory  and  leaving  them  over  night  in  a  dish  of  water. 
Often  they  will  collect  at  the  side  of  the  glass  next  to  the  hght. 

(/)  With  sharp  scissors  cut  off  as  much  as  possible  of  the 
mycelium  (fungous  threads)  of  Saprolegnia  growing  on  a  fly  or 
piece  of  meat  thrown  into  a  dish  of  algae.  Place  it  in  a  dish  of 
clean  water  and  after  a  few  hours  hang  a  small  piece  of  meat  in 
the  water  at  one  side  of  the  dish.  After  a  comparatively  short 
time  the  zoospores  produced  will  be  found  congregated  around 
the  meat  (chemotaxis). 

177.  Turgor  Movements.  Many  plant  organs  change 
their  position  or  become  curved  by  the  change  in  turgor 
of  the  cells  on  one  or  both  sides  of  the  organ.  Thus  at 
the  base  of  the  petiole  of  the  leaf  of  the  sensitive  plant 
{Mimosa  pudicd)  there  is  a  strongly  developed  mass 
of  thin-walled  cells,  the  pulvinus.  When  the  cells  on  the 
lower  side  are  turgid  the  leaf  is  held  out  horizontally  or 
inclined  upward.  In  response  to  various  stimuli  these 
cells  suddenly  allow  their  water  to  escape  into  the 
intercellular  spaces,  thus  losing  their  turgor  and  contract- 
ing considerably.  Apparently  the  cells  on  the  upper 
side  of  the  pulvinus  take  up  this  water  very  quickly, 
thus  becoming  turgid  in  their  turn.  This  process  takes 
place  very  rapidly  and  results  in  a  quick  dowmward 
bending  of  the  leaves.  It  is  by  a  similar  arrangement 
that  the  two  halves  of  the  leaf  of  the  Venus  fly-trap 
{Dionaea  muscipula)  snap  together  quickly  enough  to 
catch  insects  lighting  upon  them,  or  that  in  the  case  of 
the  sundew  (Drosera),  when  an  insect  is  caught  by  the 
sticky  mass  on  one  of  the  so-called  tentacles,  the  ad- 
jacent ones  bend  over  until  they  too  touch  the  un- 
fortunate victim  and  the  whole  leaf  gradually  closes  in 
on  it.  The  movement  of  the  stamens  in  the  flower  of 
barberry  (Berberis)  is  also  due  to  turgor  changes  as  are 


TURGOR  MOVEMENTS  121 

the  constant  movements  of  the  lateral  leaflets  of  the 
leaves  of  the  telegraph  plant  {Desmdoium  gyrans). 

178.  Some  turgor  movements  are  so-called  auton- 
omous movements;  i.e.  they  seem  to  be  due  to  internal 
causes  and  not  caused  by  external  stimuli.  Such  seems 
to  be  the  case  in  the  movements  of  the  leaflets  of  Des- 
modium  referred  to  above.  The  haflets  of  red  clover 
{Trifolium  pratense)  show  a  similar  rising  and  falling, 
but  instead  of  requiring  only  a  few  seconds  as  is  the  case 
with  Desmodium,  require  several  hours.  It  is  possible 
that  these  so-called  autonomous  movements  are  due  to 
external  stimuli  which  have  not  yet  been  recognized. 

179.  Most  turgor  movements  are  in  response  to 
some  recognized  stimulus.  Whereas  the  hygroscopic 
movements  are  the  direct  physical  result  of  the  in- 
creased or  decreased  moisture  in  the  surrounding  air, 
the  movements  in  response  to  a  stimulus  are  not  the 
direct  physical  effects  of  the  energy  exerted  by  the 
stimulus  but  are  due  to  energy  stored  up  in  the  tissues 
which  is  released  by  the  stimulus  as  the  energy  of  the 
gunpowder  is  released  by  the  chain  of  events  between  the 
pulling  of  the  trigger  and  the  discharge  of  the  gun.  As 
the  strength  with  which  the  trigger  is  pulled  has  no 
influence  upon  the  energ}^  applied  to  the  bullet,  so  the 
intensity  of  the  stimulus  has  no  direct  effect  upon  the 
vigor  of  the  movement  resulting  from  it  (except  in  so  far 
as  a  more  vigorous  stimulus  may  reach  more  cells  and  so 
release  more  energy  in  that  way). 

180.  The  most  frequent  stimuli  for  turgor  movements 
are  variations  in  temperature  and  light.  Examples  of 
this  are  the  so-called  sleep  movements  of  leaves  of  clover, 
Oxalis,  Mimosa,  etc.,  and  probably  all  leaves  that  have  a 
pulvinus  at  the  base  of  the  leaflets  or  of  the  petiole. 
On  the  other  hand  the  sudden  movements  of  the  stamens 


122  PLANT  PHYSIOLOGY 

of  barberry,  the  rapid  closing  of  the  leaf  halves  of 
Dionaea,  the  closing  of  the  leaflets  and  dropping  down- 
ward of  the  leaves  of  Mimosa  are  responses  to  the  stimulus 
of  contact.  In  the  case  of  the  sundew  the  movement  of 
the  tentacles  may  take  place  both  in  response  to  contact 
or  to  the  presence  of  certain  chemicals  such  as  ammonium 
sulphate,  proteins,  etc.  It  is  worthy  of  note  that  the 
stimulus  may  be  applied  at  a  distance  even  of  several 
centimeters  from  the  point  where  the  change  in  turgor 
occurs,  i.e.  the  plant  tissues  are  able  to  transmit  a  stimu- 
lus for  a  considerable  distance.  Kone  of  these  move- 
ments will  take  place  except  under  the  proper  degrees  of 
temperature,  moisture,  etc. 

Laboratory  Studies,  (a)  Observe  a  plant  of  Desmodium 
gijrans  at  a  temperature  of  between  20°  and  30°  C.  The 
rapidity  of  the  rotation  of  the  leaflets  will  be  found  to  vary 
with  the  temperature,  degree  of  illumination  and  other  factors. 

(6)  Observe  clover  and  Oxalis  leaves  by  night  and  by  day. 
Compare  also  the  leaves  of  Mimosa,  Robinia,  etc.,  in  light  and 
darkness. 

(c)  Touch  one  of  the  three  bristles  on  the  surface  of  a  leaf 
half  of  Venus  fly-trap  (Dionaea).  Note  the  sudden  closing  of 
the  leaf.  The  temperature  and  humidity  must  be  rather  high 
or  it  will  not  respond  well. 

{(I)  Toucli  a  leaf  of  a  sensitive  plant  {Mimosa  pudica)  at 
the  under  side  of  the  pulvinus.  Touch  or  sHghtly  pinch  other 
leaves  of  the  same  plant  at  various  points.  Apply  the  flame 
of  a  match  to  the  end  of  one  of  the  leaflets.  Note  in  this  case 
the  progressive  closing  of  the  leaflets  followed  by  the  dropping 
of  the  whole  leaf  and  in  many  cases  of  the  nearest  leaves  above 
and  below. 

(e)  Place  a  grain  of  sand  on  the  tip  of  a  tentacle  of  a  leaf  of 
sundew  (Drosera).  Note  the  degree  of  movement  in  the  sur- 
rounding tentacles.  On  a  tentacle  on  another  leaf  place  a  tiny 
piece  of  meat  or  a  very  small  crystal  of  ammonium  sulphate  and 
note  the  movements  of  the  adjacent  tentacles. 

181.  Growth  Movements.  Many  plant  movements 
are  the  result  of  unequal  growth  on  opposite  sides  of  an 


NUTATION  123 

organ.  Here  again  can  be  distinguished  autonomous 
movements  whose  stimuU  if  external  are  not  recognized 
and  paratonic  movements  in  response  to  recognized 
stimuli. 

182.  Probably  the  most  widely  prevalent  autono- 
mous growth  movement  is  that  called  nutation.  If  a 
firm  long  bristle  be  fastened  to  the  tip  of  a  growing  stem 
or  root  tip  and  its  end  be  observed  under  a  microscope 
or  in  some  cases  with  the  unaided  eye  it  will  be  found  to 
describe  a  very  irregular  somewhat  circular  figure.  This 
is  really  a  low  spiral  for  the  tip  is  advancing  at  the  same 
time  that  it  rotates.  This  is  the  form  of  nutation  that  is 
frequentl}^  called  circumnutation.  This 
movement  is  due  to  the  fact  that  the 
zone  of  most  rapid  growth  is  not  equal 
on  all  sides  but  growth  takes  place  more 
rapidly  at  one  side,  this  region  of  most 
rapid  growth  passing  around  the  stem  and 
slowly  advancing  so  that  it  remains  at  a       ^      ^„    ^• 

^  °  Fig.    53. — Cir- 

const  ant  distance  from  the  tip.     The  tip     cum  nutation 

T      1  c  1  •  1  (Ipomoea). 

is  then  bent  a  little  away  from  the  side 
where  the  most  rapid  growth  is  occurring,  hence  its  nuta- 
tion. The  opening  of  buds  is  due  to  greater  growth  on 
the  upper  than  on  the  lower  side  of  the  leaf  bases.  This 
may  be  followed  by  the  reverse  and  so  on  until  finally  a 
state  of  balance  is  reached.  This  is  another  form  of  nuta- 
tion. The  rotation  of  free  horizontal  ends  of  twining 
plants  is  often,  perhaps  not  with  correctness,  regarded  as  a 
type  of  nutation.  When  such  a  rotating  shoot  strikes  a 
vertical  support  it  keeps  on  rotating  and  thus  winds 
around  the  support  while  at  the  same  time  its  negatively 
geotropic  response  (see  paragraph  186)  is  sufficient  to 
cause  the  stem  to  ascend  spirally.  IMost  ]ilants  rotate  in 
a  direction  opposite  to  that  of  the  hands  of  a  watch  when 


124  PLANT  PHYSIOLOGY 

seen  from  above,  but  a  few  plants  rotate  in  the  opposite 
direction.  Some  botanists  regard  the  whole  rotary 
movement  of  such  plants  not  as  a  form  of  nutation  but 
as  a  special  form  of  geotropic  response. 

183.  Those  growth  movements  due  to  the  response 
to  recognized  stimuli  are  often  divided  into  tropic 
movements  where  the  organ  affected  is  brought  to  lie 
with  its  axis  in  some  definite  relation  to  the  direction  of 
the  stimulus,  and  nastic  movements  where  one  or  the 
other  face  of  a  bifacial  organ  is  placed  in  some  relation  to 
the  direction  of  the  stimulus.  However,  in  view  of  the 
fact  that  the  general  phenomena  concerned  are  the  same, 
the}^  need  not  be  sharply  separated  here. 

184.  The  chief  tropic  movements  of  plants  are 
phototropism,  geotropism,  thigmotropism,  chemotropism, 
being  responses  respectively  to  the  stimulus  of  light, 
gravity,  contact  and  chemical  substances.  Other  tro- 
pisms  have  been  distinguished  but  will  not  be  discussed 
here.  For  all  tropisms  the  point  of  curvature  is  the 
region  where  the  most  rapid  growth  usually  occurs.  As 
the  result  of  the  stimulus  the  growth  is  increased  above 
the  normal  rate  on  one  side  and  sometimes  even  retarded 
below  the  normal  on  the  other  with  the  result  that  a 
curvature  is  produced.  The  perceptive  region  for  the 
stimulus  may  be  distant  some  millimeters  or  even 
centimeters  from  the  zone  of  growth. 

185.  Phototropism  may  be  illustrated  by  the  action  of 
a  plant  illuminated  on  one  side  only.  Usually  the 
stem  of  such  a  plant  curves  toward  the  source  of  light 
(positive  phototropism)  while  the  leaves  place  themselves 
so  as  to  stand  with  their  surfaces  at  right  angles  to  the 
source  of  the  light  (photonasty).  Sometimes  the  cur- 
vature is  away  from  the  light  as  is  the  case  with  most 
roots  and  with  the  stems  of  some  climbing  plants,  e.g. 


GEOTROPISM  125 

ivy  (Hedera  helix).  This  is  negative  phototropism. 
Too  great  intensity  of  light  may  cause  a  positively 
phototropic  organ  to  become  negatively  phototropic. 
A  very  small  amomit  of  light  scarcely  perceptible  to 
the  human  eye  is  sufficient  to  induce  phototropic  cur- 
vature in  some  plants.  The  effective  rays  of  light 
are  those  of  the  blue  and  violet  portion  of  the  spec- 
trum. The  perceptive  region  may  be  some  distance 
from  the  region  of  curvature.  Thus  in  the  seedlings  of 
oats  the  tip  of  the  first  leaf  is  the  perceptive  region  while 
the  curvature  takes  place  at  a  point  near  the  ground. 

186.  Geotropism.  If  a  seedling  that  usually  grows 
upright  be  placed  in  a  horizontal  position  for  a  few  hours 
the  tip  of  the  stem  will  be  found  to  be  curved  so  as  to  be 
directed  upward,  while  the  tip  of  the  root  will  have 
assumed  a  position  directed  downward,  the  remainder 
of  the  stem  and  roots  being  horizontal.  If  the  root  tip 
and  stem  tip  have  been  previously  marked  with  cross 
lines  at  equal  distances  it  will  be  found  that  the  curvature 
begins  and  is  carried  out  by  those  regions  of  stem  and  root 
respectively  where  the  growth  is  usually  most  rapid  and 
the  curvature  has  taken  place  by  the  more  rapid  growth 
on  one  side  than  on  the  other.  The  main  root,  then,  is 
positively  geotropic  and  the  stem  negatively  so. 

187.  If  the  plant  has  been  allowed  to  grow  until 
horizontal  lateral  roots  have  been  produced  and  then  is 
placed  with  the  main  stem  horizontal  it  will  be  found 
that  not  only  does  the  main  stem  curve  upward  and  the 
main  root  downward,  but  that  the  lateral  roots,  which 
are  now  of  course  some  of  them  directed  upward  and  some 
downward,  wnll  curve  so  as  to  occupy  a  horizontal  position 
again.  Thus  it  is  apparent  that  some  stimulus  causes 
certain  plant  parts  to  grow  toward,  other  parts  away  from 
and  still  others  parallel  to  the  surface  of  the  earth.    Care- 


126  PLANT  PHYSIOLOGY 

ful  experiments  have  shown  that  it  is  with  reference  to 
the  direction  of  the  force  of  gravity  that  these  different 
plant  parts  orient  themselves. 

188.  Experiments  have  shown  that  by  attaching 
plants  to  a  rapidly  whirling  wheel  the  centrifugal  force 
has  the  same  effect  as  gravity  and  stimulates  the  main 
root  growth  away  from  the  center  of  the  wheel,  while 
the  growth  of  the  main  stem  becomes  directed  toward 
the  center  and  that  of  the  lateral  roots  at  right  angles 
to  the  radius.  On  the  other  hand,  if  the  wheel  to  which 
a  plant  is  attached  be  rotated  very  slowly  with  its  axis 
horizontal  so  that  all  sides  of  the  plant  are  successively 
exposed  to  the  stimulus  of  gravity,  the  rotation  being  so 
slow  that  the  centrifugal  force  is  negligible,  the  different 
parts  of  the  plant  continue  to  grow  in  any  direction  they 
may  have  happened  to  start.  It  is  thus  apparent  that 
the  general  form  of  the  plant  is  largely  controlled  by 
the  stimulus  of  gravity  as  well  as  by  the  stimulus  of 
light. 

189.  The  zone  of  curvature  is  that  of  most  rapid 
growth.  The  perceptive  region  may,  how^ever,  be  dis- 
tant some  millimeters.  Thus  in  the  root  it  has  been 
shown  that  the  root  cap  is  the  region  of  greatest  percep- 
tion. It  has  been  suggested  that  the  cells  there  contain- 
ing starch  grains  are  the  perceptive  cells,  the  different 
position  in  the  cell  assumed  by  these  starch  grains  in 
response  to  gravity  as  the  root  is  pointed  in  various 
directions  furnishing  the  stimulus  which  is  communi- 
cated from  cell  to  cell  to  the  growing  zone.  Here  cer- 
tain cells  on  one  side  are  stimulated  to  grow^  more  rapidly 
than  those  on  the  opposite  side  until  the  root  has  assumed 
its  proper  position,  when  the  starch  grains  (statoliths) 
will  resume  their  normal  position  in  the  perceptive  cells. 
The  similar  starch-bearing  cells  in  the  perceptive  regions 


THIGMOTROPISM,  CHEMOTROPISM  127 

of  stems  have  also  Iwcn  supposed  to  be  such  ''statocysts. '' 

190.  Thigmotropism.  If  a  tendril  be  touched  on  one 
side  by  some  uneven  object  (not  by  a  smooth  object 
like  a  very  smooth  rod  or  a  drop  of  water  or  mercury),  it 
begins  to  curve  very  soon  in  the  direction  of  that  object. 
At  the  very  first  this  curvature,  which  may  become 
apparent  within  a  few  seconds,  is  undoubtedly  due  to 
changes  in  turgor  on  the  two  sides  of  the  tendril,  but  in 
only  a  short  time  rapid  growth  sets  in  on  the  outside,  and 
the  tendril  winds  around  the  object.  Soon  thereafter  the 
part  of  the  tendril  between  the  stem  and  the  object  also 
begins  to  coil  in  a  double  spiral,  this  also  being  due  to 
unequal  growth.  Thigmotropism,  as  this  phenomenon 
is  called,  is  exhibited  by  tendrils  and  by  other  parts  of 
plants  that  assume  this  function,  such  as  the  leaf  stalk  of 
Clematis,  peduncles  of  some  plants,  and  whole  shoots, 
especially  modified  for  this  purpose,  of  other  plants. 
Special  papilla-like  cells  have .  been  regarded  by  some 
botanists  as  the  organs  of  perception.  The  curvature  of 
roots  toward  or  away  from  points  of  injury  is  possibly  to 
be  considered  as  a  special  form  of  thigmotropism.  It  is 
often  called  traumatropism. 

191.  Chemotropism.  The  hyphae  (filaments  of  cells)  of 
many  fungi  and  the  i)ollen  tubes  of  seed  plants  show  a 
peculiar  growth  response  to  the  stimulus  of  various 
chemical  substances.  Thus,  many  pollen  grains  placed 
on  a  piece  of  moist  filter  paper  will  produce  tubes 
growing  in  any  direction,  but  if  a  small  crystal  of  cane 
sugar  be  placed  on  the  paper,  some  kinds  of  pollen 
tubes  will  change  their  direction  of  growth  and  turn 
directly  toward  it.  Fungus  hyphae  show  similar  changes 
in  direction  of  growth  when  they  perceive  various  sub- 
stances in  solution.  In  both  cases  certain  substances 
induce     positive    and     others    negative    chemotropism. 


128  PLANT  PHYSIOLOGY 

Of  the  same  general  class  of  phenomena  is  the  so-called 
hydrotropism,  in  which  roots  grow  away  from  the  dry 
and  toward  the  moist er  air. 

192.  In  all  these  tropisms  the  stimulus  must  be  of  a 
certain  strength,  or  it  is  not  perceived.  Even  if  strong 
enough  to  be  perceived,  the  stimulus  must  act  for  a 
certain  length  of  time  before  the  plant  has  been  suffi- 
ciently affected  to  bring  about  a  reaction.  The  stronger 
the  stimulus  (up  to  a  certain  point),  the  shorter  the  time 
that  is  necessary  for  it  to  act.  The  reaction  to  the  stimu- 
lus may  be  almost  immediate,  or  it  may  not  show  itself 
for  some  time.  In  fact,  the  stimulus  may  have  ceased  to 
act  upon  the  plant  for  some  httle  time  before  the  plant 
shows  any  response.  Thus  a  root  may  be  placed  in  a 
horizontal  position  for  fifteen  to  twenty  minutes  and  then 
restored  to  its  normal  vertical  position.  After  a  little 
while  the  root  will  begin  to  curve  and  will  attain  quite  a 
marked  curvature  until  the  stimulus  then  produced  by 
the  resulting  abnormal  position  induces  the  root  to  curve 
back  again.  In  this  case  it  usually  swings  too  far  in  the 
other  direction,  and  does  not  finally  attain  its  normal 
position  until  it  has  made  several  such  swings.  Similar 
results  can  be  obtained  with  phototropism. 

193.  Among  the  nastic  movements  are  the  opening 
and  closing  of  flowers,  in  response  to  changes  in  tempera- 
ture or  illumination.  These  are  accomplished  by  in- 
creased growth  at  the  base  of  the  petals  and  sepals  on 
the  inner  or  outer  sides  respectively.  A  change  of  tem- 
perature of  only  one  or  two  degrees  is  sufficient  in  the 
case  of  the  tulip  to  stimulate  the  flower  to  open  or  close, 
as  the  case  may  be.  Many  plants,  as  long  as  their  leaves 
are  still  capable  of  growth,  show  so-called  sleep  move- 
ments, which  are  not,  like  those  of  the  clover  (see  para- 
graph 180),  due  to  changes  in  turgor,  but  to  more  rapid 


NASTIC  MOVEMENTS  12!) 

growtli  on  one  or  the  other  side  of  the  base  of  the  petiole. 
Such  responses  to  changes  in  Hght  and  temperature  cease 
when  the  leaves  have  attained  full  growth,  while  those 
due  to  turgor  changes  in  the  leaves  that  have  pulvini 
persist. 

Laboratory  Studies,  (a)  Fix  a  slender  filament  of  glass  or  a 
stiff  bristle  to  the  rapidly  growing  end  of  a  shoot  of  Fuchsia, 
geranium  (Pelargonium),  or  verbena,  using  a  drop  of  thick 
shellac  glue.  Support  a  plate  of  glass  in  a  horizontal  position, 
just  above  the  tip  of  the  pointer,  and  record,  by  making  ink 
dots  on  the  glass,  the  position  of  the  pointer  at  definite  inter- 
vals of  time,  say  every  ten  minutes.  A  microscope  may  be 
focused  upon  the  tip  of  the  pointer  and  the  movement  observed 
in  this  way.  In  this  and  similar  experiments  the  illumination 
should  be  as  nearly  equal  as  possible  on  all  sides. 

(6)  In  a  similar  manner,  the  nutator}'-  movements  of  a  Iciif 
may  be  observed  by  fastening  a  pointer  to  its  tip,  and  observing 
it  with  a  horizontal  microscope  or  by  recording  the  position  of 
the  pointer  at  successive  intervals  on  a  vertical  glass  plate. 

(c)  Nutation  can  be  demonstrated  also  in  the  long  stout 
roots  from  seedlings  of  beans,  peas,  etc.  These  should  be 
placed  so  as  to  point  directly  downward,  so  as  to  avoid  geo- 
tropic  curvature.  The  movement  can  be  observed  by  placing 
a  mirror  at  an  angle  of  45  degrees  under  the  tip,  and  focusing  a 
horizontal  microscope  on  the  tip  as  reflected  in  the  mirror. 

(d)  Observe  the  rotatory  movements  of  the  horizontally 
bent  end  of  a  shoot  of  morning-glory  (Ipomoca)  or  hop  (Humu- 
lus).  Note  the  time  required  to  make  a  complete  revolution. 
The  stem  also  nuist  twist  one  whole  revolution 

for  every  turn  the  tip  makes.  Place  an  upright 
stake  in  the  way  of  the  shoot,  and  note  how  the 
climbing  takes  i)lace. 

(<?)  Germinate  a  mustard  or  sunflower  seed 
in  the  dark,  and  after  the  cotyledons  have 
escaped  from  the  seed  coat,  place  the  seedling 


in  a  hole  in  a  cork,  so  that  tiie  root  i)rojects     Fh-  o4.— Phoio- 
below  and  the    cotyledons    above.      Put    the  ^j;op'=^'"*^^i'^""'"^*"^ 
cork  in  a  bottle  so  that  the  tip  of  the  root 
dips  into  water,  or  better  stifl,  into  a  nutrient  solution  (see 

9 


130  PLANT  PHYSIOLOGY 

laboratory  study  (b)  after  paragraph  146).  Keep  in  the  dark 
until  the  stem  and  roots  are  both  in  a  vertical  position.  Place 
in  a  box,  closed  on  all  sides,  except  for  an  opening  about  10 
mm.  wide  at  one  side,  and  direct  this  opening  toward  a  win- 
dow. Note  the  direction  of  curvature  of  stem  and  roots,  as 
well  as  the  region  where  the  curvature  occurs. 

(/)  Perform  experiments  similar  to  the  foregoing,  placing 
orange-red  glass  or  deep  blue  glass  in  front  of  the  opening,  and 
note  the  results. 

(g)  Sterilize  some  fresh  horse  manure  in  a  steam  sterihzer 
to  destroy  all  the  fungi,  and  inoculate  with  the  manure  mold, 
Pilobolus.  When  the  sporangia  of  this  are  about  to  be  formed, 
place  the  dish  containing  the  culture,  micovered,  in  a  dark  box, 
tilting  the  dish  at  an  angle  of  45  degrees  toward  one  side,  where 
a  small  window  about  2.5  cm.  in  diameter  is  left  open  to  admit 
light,  but  covered  on  the  inside  with  a  glass  plate.  Place  the 
box  in  such  a  position  that  the  Hght  can  enter  the  window.  The 
sporangia  will  direct  themselves  toward  the  light  and  discharge 
their  spore  masses,  which  will  stick  to  the  glass  covering  the 
window.  Only  a  few  shots  will  fail  to  hit  the  ''bull's  eye" 
if  the  distance  from  the  dish  of  the  fungus  to  the  window  is 
not  more  than  10  to  20  cm.,  although  these  are  discharged  with 
considerable  accuracy  much  further  than  that.  Try  the  effect 
of  different  colored  glass  on  the  accuracy  of  the  aim. 

(h)  Germinate  a  number  of  seeds  of 
broom-corn  millet  or  proso  {Panicum 
miliaceum)  in  the  dark,  in  a  pot  of  earth. 
When  they  have  attained  a  length  of  1  to 
2  cm.,  cap  the  tips  of  half  of  the  seed- 
lings with  httle  caps  of  tinfoil,  made  over 
the  point  of  a  pencil,  and  then  gently 
Fig.  o5.-Phototropi3m  ^lippcd  ovcr  the  tip  of  the  sccdling  and 
experiment  {h).  pinchcd  in  placc.     Set  the  pot  in  the 

box  used  for  experiment  (e),  and  note  the 
result.  Almost  as  good  results  can  be  obtained  by  using  oats. 
{i)  Germinate  seeds  of  bean,  sunflower,  mustard,  etc.  After 
the  seedlings  show  well-developed  cotyledons,  fasten  several  of 
them  by  their  middles  in  a  horizontal  position,  under  a  bell-jar 
over  water,  so  as  to  keep  the  air  moist  and  prevent  the  seeds 
from  drying  out.  Keep  in  a  dark  place  for  a  few  hours  and  note 
the  results. 


LABORATORY  STUDIES  131 

0')  Grow  a  bean  seedling  in  water  culture  until  some  of  the 
horizontal  roots  have  developed  a  little  way.  Then  place  the 
main  root  horizontally  as  in  (i).  Note  the  effect  on  the  main 
and  lateral  roots  and  stem. 

(k)  Plant  seeds  of  Indian  corn  or  beans  1  or  2 
cm.  beneath  the  surface  of  the  soil,  in  a  completely 
filled  flower  pot.  Fasten  a  coarse  wire  netting  over 
the  top  of  the  pot,  and  invert  it,  putting  it  on  an 
iron  tripod,  standing  in  a  plate  of  water,  and  place  a 
bell  jar  over  the  whole,  to  keep  the  air  moist.  After 
a  few  days  the  roots  will  emerge  from  the  soil  into  the 
air  in  response  to  the  stimulus  of  gravity,  while  the  menuiT."" 
stems  grow  on  up  into  the  soil. 

(l)  Place  a  flower  pot  with  a  growing  plant  in  a  horizontal 
position.  At  the  same  time  place  another  one  with  a  similar 
plant  horizontally  in  a  khnostat,  so  that  it  rotates  slowly  with 
the  axis  of  rotation  horizontal.  Keep  both  in  a  dark  room 
twenty-four  hours  during  the  process,  and  then  compare  the 
plants.  (A  klinostat  is  an  apparatus  worked  by  clock-work, 
which  rotates  a  flower  pot  fastened  to  it  at  a 
slow  rate,  being  arranged  so  that  the  axis  of 
rotation  may  be  in  any  direction  desired.  A 
simple  klinostat  can  he  made  by  removing 
the  longer  hand  of  a  clock  and  fastening  to  the 
Fig.  57.— Geo-  pinion  a  stiff  horizontal  wire,  supported,  if  need 
menrcJ).  ^^^^""  bc,  at  the  other  end.  At  the  middle  of  the 
wire  may  be  placed  a  large  cork,  to  which  seed- 
lings can  be  attached.  With  a  small  clock  it  is  impossible  to 
use  a  flower-pot,  as  it  is  too  heavy,  and  so  instead  the  seedlings 
will  be  fastened  to  the  edge  of  the  cork,  and  since  they  are 
exposed  to  the  stimulus  of  gravity  from  successively  different 
directions,  they  will  show  no  gcotropic  curvature.  In  home- 
made apparatus  of  this  kind  the  portion  including  the  cork 
with  the  attached  plants  ought  to  be  so  enclosed  that  the  plants 
will  not  dry  out.) 

(m)  Place  seedlings  at  the  edge  of  a  horizontal  wheel  that 
can  be  rotated  very  rapidly  (centrifugal  apparatus).  When  the 
centrifugal  force  much  exceeds  the  force  of  gravity,  the  roots 
will  grow  almost  directly  outward  and  the  stems  almost  directly 
inward.  If  both  are  equal,  the  roots  will  be  directed  downward 
and  outward  at  an  angle  of  45  degrees,  and  the  stem  upward 


132  PLANT  PHYSIOLOGY 

and  inward  at  the  same  angle.     If  the  wheel  is  rotated  in  a 
vertical  plane,  the  effect  of  gravity  is  entirely  eliminated,  for 
it  acts  on  all  sides  in  succession,  and  it  is  only  the  centrifugal 
force  that  comes  into  play.     (Such  an  apparatus  with  the  wheel 
rotating  in  the  vertical  plane   can   be    con- 
structed by  using  a  stout  knitting  needle  for 
an  axis,  the  bearings  being  little  cups  of  glass 
made  by  sealing  and  cutting  off  short  the  end 
of  a  glass  tube.     These  are  inserted  into  corks, 
fastened  to  two  upright   supports.      At   the 
center  of  the  knitting  needle  is  placed  a  large 
cork  with  short  knitting  needles  radiating  in 
troTsnf^'ex^eri-  ^^^^  directions  in  a  plane  at  right  angles  to 
ment  (m).  the  main  axle.    The  ends  of  these  hold  corks, 

which  are  connected  to  each  other  by  a  wire, 
which  forms  the  circumference  of  the  wheel.  On  this  wire  are 
strung  a  number  of  small  cork  disks.  A  stream  of  water  is 
directed  at  these  disks,  and  causes  the  wheel  to  rotate  at  a  high 
speed.  Seedlings  to  be  experimented  with  are  pinned  firmly 
to  the  cork  disks.) 

(n)  IMake  a  thin  section  of  a  root  cap  of  a  growing  root, 
stain  with  iodine  to  make  the  starch  grains  more  ea^y  visible, 
The  cells  containing  them  are  supposed  by  some  botanists  to 
be  the  perceptive  cells  for  gravity  (statocysts). 

(o)  On  a  vigorous  plant  of  cucumber  or  squash  or  pea,  make 
the  following  experiment  with  the  tendrils.  Place  a  very 
smooth  glass  rod  in  contact  with  one  tendril,  and  a  rough  stick 
of  the  same  diameter  in  contact  with  another  equally  developed 
one.  Note  the  time  in  each  case  before  the  first  curvature  is 
noticeable  and  until  the  tendril  has  made  one  complete  turn 
around  the  object.  Note  wdien  the  formation  of  the  coils 
between  the  object  and  point  of  attachment  of  the  tendril 
first  begins,  and  observe  how  a  twisting  of  the  tendril  is  avoided 
as  these  coils  develop. 

{]))  Wet  a  piece  of  filter  paper  with  Sachs'  culture  solution 
and  sow  on  it  fresh  pollen  grains  of  various  kinds,  keeping  the 
different  kinds  on  different  parts  of  the  paper,  but  all  at  about 
the  same  distance  from  the  center.  Cover  to  prevent  evapo- 
ration. After  a  few  hours,  examine  and  if  germination  has 
occurred,  place  a  small  crystal  of  cane  sugar  at  the  center. 
Examine  every  two  or  three  hours,  and  note  when  and  where 


PATHOLOGY  133 

and  for  what  kind  of  pollen  clicniotroi)ism  first  boconies  ai^jKir- 
ent.  The  experiment  can  be  varied  by  placing  the  stigmas  of 
one  of  the  flowers  at  the  center  instead  of  the  crystal  of  sugar. 
It  will  attract  some  of  the  kinds  of  pollen  tubes  and  have  no 
effect  on  others.  (The  pollen  grains  and  their  germination 
can  be  observed  much  more  easily  if,  in  place  of  the  filter  paper, 
the  following  be  used:  To  a  measured  quantity  of  boiling  culture 
solution,  sift  in  with  constant  stirring  enough  agar  powder  to 
make  a  2  per  cent,  solution.  When  thoroughly  dissolved,  pour 
it  into  petri  dishes  and  cover,  and  allow  to  cool.  On  the  jell}-- 
like  mass  thus  produced  the  germination  of  pollen  grains  can 
be  observed  very  easily.) 

(q)  In  the  spring  bring  into  the  laboratorj^  buds  of  tulij)  or 
crocus,  just  about  to  open.  In  the  w'armer  air  thc}^  will  soon 
open  by  increased  growth  on  the  inner  surface  of  the  bases  of 
the  petals  and  sepals.  When  fully  opened,  place  in  an  ice-box 
or  out-of-doors  on  the  window  ledge,  and  ver}^  soon  increased 
growth  on  the  outside  will  cause  them  to  close. 

(r)  Observe  growing  plants  of  sunflower  (Helianthus),  lamb's 
quarters  (Chenopodium),  etc.,  by  day  and  by  night,  and 
notice  the  different  leaf  positions  assumed  by  the  younger 
leaves.  The  fully  developed  leaves  will  show  little  or  no  change 
of  position. 

194.  Pathology  is  the  study  of  the  abnormal  develop- 
ment and  functioning  of  a  plant.  It  is  in  its  widest  as- 
pect abnormal  physiology.  As  usually  studied,  however, 
it  is  the  determination  of  the  cause  of  and  means  of  pre- 
vention of  certain  plant  diseases.  Since  most  plant 
diseases  that  have  been  studied  are  caused  by  fungi, 
pathology  as  taught  is  often  but  a  study  of  mycology,  in 
which  parasitic  fungi  alone  are  considered.  These  views 
of  pathology  are  in  reality  only  partial  views,  and  do  not 
take  the  real  scope  of  the  subject  into  consideration. 

195.  Since  abnormal  functioning  often  leads  to  abnor- 
mal structural  development  it  is  necessary  to  study  not 
only  the  al)normal  functioning  of  a  plant  but  also  the 
abnormal  structures  produced  by  the  diseased  conditions. 
Thus  we  can  distinguish  cases  in  which  cells  or  tissues  do 


134  PLANT  PHYSIOLOGY 

not.  reach  their  full  size  or  number  (hypoplasy),  orinwhich 
individual  cells  or  whole  tissues  are  enlarged  above  the 
normal  size  (hypertrophy),  or  in  which  the  cells  are  ab- 
normally increased  in  number  (hyperplasy).  In  some 
cases  cells  destined  to  produce  one  kind  of  tissue  are 
changed  into  other  kinds  by  the  pathological  conditions. 
Furthermore,  the  internal  structures  of  the  cell  may  be 
modified.  The  chloroplasts  may  be  increased  in  number 
and  size  or.  diminished  or  apparently  wholly  suppressed. 
The  nucleus  may  be  enlarged  and  changed  in  shape  or 
caused  to  divide  abnormally  so  that  multinucleate  cells 
result.  The  contents  of  the  cells  are  often  modified; 
acids  may  be  increased  or  diminished;  the  tannin  content 
may  increase  remarkably  in  some  cases  as  also  that  of 
various  coloring  matters  or  of  various  enzymes. 

196.  These  changes  are  in  some  cases  the  results  of 
causes  not  as  yet  recognizable.  Such  troubles  are  spoken 
of  as  ''Physiological  Diseases,"  this  being  simply  a  name 
to  cloak  our  ignorance  of  the  true  cause  of  the  trouble. 
In  many  cases,  however,  the  changes  occur  as  a  result  of 
the  action  of  parasitic  organisms,  either  plant  or  animal 
in  nature.  In  the  case  of  many  inj  uries  caused  by  animals 
(e.g.  biting  insects)  the  injury  is  chiefly  mechanical  and  is 
a  subject  for  study  from  the  standpoint  of  pathology  in 
just  the  same  way  as  the  study  of  wounds  caused  by  other 
agencies.  But  the  punctures  of  some  insects  (e.g.  plant 
lice,  aphids)  are  followed  by  marked  physiological  dis- 
turbances in  the  cells  immediately  or  even  remotely  ad- 
jacent to  the  punctures,  leading  to  the  type  of  disease 
called  stigmonose  (or  puncture  disease) .  The  enormously 
varied  structures  found  in  insect  galls  as  a  result  of  the 
presence  or  punctures  of  various  gall-producing  insects, 
if  properly  understood,  would  doubtless  throw  a  flood  of 
light  upon  the  subject  of  pathology  and  even  physiology. 


PATHOLOGY  135 

In  all  these  cases  it  is  not  the  parasite  but  its  effect  upon 
the  host  that  should  be  the  subject  of  pathological  in- 
vestigation by  the  botanist.  It  must  be  remembered 
that  merely  to  learn  the  name  of  the  organism  causing  the 
pathological  change  in  a  plant  is  not  to  study  pathology. 
It  is  the  investigation  of  the  actual  physiological  and 
structural  changes  in  the  diseased  tissues  that  deserves 
that  name. 

197.  By  far  the  greater  number  of  plant  diseases 
hitherto  investigated  are  those  caused  by  parasitic  plants 
(bacteria,  fungi  and  flowering  plants).  As  in  the  case  of 
injury  by  animal  parasites  the  effects  are  very  varied. 
Thus  with  some  parasites  the  injury  consists  of  perhaps 
hardly  more  than  the  withdrawal  of  food  stuffs  or  water 
from  the  tissues  of  the  host.  Usually,  however,  the  case 
is  not  so  simple.  There  is  almost  always  some  mechanical 
disturbance  as,  for  example,  the  destruction  of  the  middle 
lamella  to  permit  the  intercellular  growth  of  a  fungus 
hypha  or  perhaps  the  actual  crushing  of  some  of  the  cells 
of  the  host  by  the  roots  of  some  of  the  parasitic  flowering 
plants.  A  few  parasites  kill  the  cells  some  distance  in 
advance  of  their  progress  by  the  secretion  of  poisons  of 
various  kinds  (as  is  the  case  with  Sclerotinia  lihertiana), 
feeding  then  upon  the  more  or  less  disorganized  remains 
of  the  dead  cells.  In  other  cases,  however,  the  parasite 
does  not  kill  the  host  cells  outright  but  sends  little 
branches  (haustoria)  into  them  through  which  the  food 
matters  are  gradually  absorbed,  the  death  of  the  cell 
perhaps  being  delayed  for  a  long  period  during  which  it  is 
constantly  furnishing  food  to  its  parasite.  Sometimes 
the  diseased  tissues  become  enlarged  and  richly  stored 
with  food  (various  fungus  galls,  e.g.  peach  leaf  curl  due  to 
Exoasciis  dejormans)  which  may  then  be  used  by  the 
fungus. 


136  PLANT  PHYSIOLOGY 

198.  Death  of  the  diseased  phiiit  or  tissues  may  be  very 
early  or  may  actually  be  postponed  beyond  the  normal 
time,  the  fungus  continuin<^  to  live  in  the  living  infected 
tissues  after  the  surrounding  tissues  are  dead.  In  most 
cases,  however,  the  presence  of  the  parasite  so  weakens 
the  host  that  part  of  it  or  even  the  whole  plant  dies.  The 
death  may  result  from  various  causes.  Thus  a  disease 
involving  the  tissues  of  the  roots  may  so  interfere  with  the 
al)sorption  of  water  that  the  top  of  the  pLant  dies  under 
symptoms  of  wilting.  It  is  sometimes  hard  to  tell, 
however,  whether  the  wilting  is  really  due  to  reduced 
water  supply  from  the  roots  or  to  poisons  secreted  by  or 
whose  secretion  is  induced  by  the  fungus  so  that  the  cells 
of  the  top  are  poisoned  and  lose  their  turgor,  i.e.  wilt. 
Or  again,  the  leaf  tissues  may  be  so  destroyed  by  the  in- 
vasion of  a  fungus  that  photosynthesis  is  not  sufficient 
and  the  plant  is  weakened  and  dies.  In  some  cases  the 
mechanical  rupture  of  the  host  tissues  by  the  reproduc- 
tive bodies  of  the  parasites  leads  to  the  destructive  loss  of 
water  through  the  wounds  thus  formed.  This  is  probably 
why  the  black  stem  rust  of  grains  {Pucdnia  graminis)  is 
so  destructive. 

199.  External  meteorological  conditions  often  result  in 
harmful  conditions  in  the  plant.  Thus  low  temperature, 
even  when  the  freezing  point  is  not  approached,  may  so 
check  certain  functions  that  a  plant  remains  dwarfed  or 
pale  (as  in  Indian  corn  in  a  cold  spring).  Excessive  heat 
and  atmospheric  dr3'ness  ma}"  cause  so  much  water  loss 
that  the  plant  actually'  dries  out  and  dies.  But  aside 
from  these  cases  must  ])e  noted  the  diseased  conditions 
resulting  from  harmful  substances  in  the  air.  Thus  in 
the  vicinity  of  manufacturing  cities  some  trees  cannot 
exist,  owing  to  the  sulphur  dioxide  given  out  in  the  smoke 
and  which  gradually  poisons  some  of  the  nutritive  cells 


PATHOLOGY  137 

of  tlie  leaves.  Some  of  the  eon.stitueiits  of  illumiiuLtin^ 
gases  in  the  air  or  in  the  soil  are  frequent  sources  of  injury 
and  death  of  plants. 

200.  The  question  of  the  relative  susceptibility  of 
plants  to  attack  by  parasites  is  also  comprehended  in  the 
term  pathology.  As  yet  it  is  not  clear  whj^  certain  phmts 
are  nearly  immune  and  other  plants  of  the  same  species 
are  very  susceptible  to  a  certain  disease.  Apparently  the 
difTerence  is  due  parth^  to  differences  in  structure  and 
partly  (perhaps  chiefiy)  to  slight  differences  in  the  chem- 
ical composition  of  the  protoplasm  or  cell  sap.  The 
question  of  induced  immunit}^  the  effect  of  changed 
external  conditions  upon  susceptibility  to  injury,  etc., 
are  very  important  fields  of  study  that  are  as  yet  almost 
uninvaded. 

201.  The  study  of  a  plant  disease  would  require  then 
that  the  student  determine  the  answers  to  the  following 
questions,  and  perhaps  others  as  well:  (1)  What  are  the 
pathological  symptoms,  both  structural  and  plwsiological  ? 
(2)  Is  the  disease  caused  by  a  parasite?  (3)  If  not  caused 
b}^  a  parasite,  what  is  the  cause?  (4)  If  caused  by  a 
parasite,  what  is  its  life  history,  particular  attention  being 
given  to  the  time  and  mode  of  entry  into  the  host,  method 
of  propagation,  over-wintering,  etc.?  (5)  What  are  the 
external  conditions,  meteorological  or  cultural,  that  favor 
or  check  the  spread  of  the  disease?  (6)  What  differences 
in  susceptibility  to  the  disease  are  found  in  different  indi- 
viduals or  strains  of  the  host?  (7)  What  is  the  history  of 
the  disease,  its  distribution,  loss  caused  by  it,  etc.?  (8) 
In  view  of  the  foregoing,  how  can  the  disease  best  be 
controlled? 

Laboratory  Studies.  It  is  iiiipossil)le  for  a  student  in  this 
stage  of  training  to  undertake  laboratory  or  field  studies  of  any 
plant  diseases.     It  may  not  be  amiss,  however,  to  have  him 


138  PLANT  PHYSIOLOGY 

collect  and  examine  as  many  different  types  of  plant  diseases 
as  he  can  find,  for  the  mere  ability  to  recognize  diseased  condi- 
tions is  of  great  value. 

REFERENCE  BOOKS 

C.  R.  Barnes,  Physiology  (in  Text-book  of  Botany  by  Coulter, 

Barnes  &  Cowles),  Chicago,  1910. 
L,  JosT,  Lectures  on  Plant  Physiology  (Engl.  Ed.,  Oxford,  1909). 
W.  Pfeffer,  The  Physiology  of  Plants  (Engl.  Ed.,  Oxford,  1900- 

1906). 
B.  M.  DuGGAR,  Plant  Physiology,  1911,  New  York. 
R.  J.  Pool  ,  Suggestions  for  Experiments  in  Plant  Physiology, 

19 U,  Lincoln. 
For  the  chemical  aspects  of  this  chapter  and  especially  for  the 

following  chapter  the  following  books  are  useful. 
Haas  and  Hill,  Introduction  to  the  chemistry  of  Plant  Products 

1913,  New  York. 
F.  CzAPEK,  Biochemie  der  Pflanzen,  1913,  Jena. 


CHAPTER  V 

THE  CHEMISTRY  OF  THE  PLANT 

In  these  paragraphs  are  brought  together  the  com- 
moner plant  constituents  and  products,  giving  the  name, 
chemical  formula  and  occurrence  of  each,  so  far  as  these 
are  known. 


Substance  and  Formula 

Water 
H2O 
Inorganic  Acids  and  Salts 


Sulphuric 

H,S04 
Nitric 

HXO3 
Hydrochloric 

HCl 


Phosphoric 
H3PO4  (and 


other  forniy) 


Occurrence 

In  all  parts  of  the  plant;  the 
chief  solvent. 

These  acids  are  present  almost 
exclusively  as  the  neutral  or 
acid  salts  of  various  metals, 
especially  Ca,  K,  Na  and  Mg. 
They  are  largely  absorbed  by 
the  plant  from  the  surround- 
ing water  in  the  forms  in  which 
they  are  present  in  the  plant, 
or  a  shifting  of  the  bases  oc- 
curs after  their  absorption. 
Chiefly  as  the  Ca  salt  in  some 
crystals. 
As  various  salts  in  the  cell  sap. 

Chiefly  as  K  or  Na  salts  in  the 
cell  sap  of  plants,  especially 
those  of  salty  soil,  or  in  ma- 
rine algae. 

In  the  cell  sap  as  Ca,  Na  or  K 
salts. 


139 


140 


THE  CHEMISTRY  OF  THE  PLANT 


Carbonic 
H2CO3 


Silicic  (of  various  forms) 
Si(0H)4,  etc. 


Organic  Acids. 


As  CaCOs  in  cyst olit lis  of 
Ficus,  and  as  deposits  in  or 
upon  the  cell  walls  of  many- 
algae  and  fungi. 
These  are  absor])ed  in  the  K, 
Na  and  Al  salts  and  are  some- 
times deposited  in  undeter- 
mined composition  in  cell 
walls,  e.g.  diatoms,  scouring 
rushes  (Equisetum),  etc. 

These  occur  in  all  parts  of  the 
plant,  either  free  or  as  esters 
or  as  salts  of  metallic  bases. 
They  are  present  as  reserve 
food,  as  waste  products,  as 
substances  to  increase  the  os- 
motic pressure,  to  increase 
acidity,  etc. 

As  free  acid  in  stinging  hairs 
of  nettles,  in  some  fruits,  etc., 
and  sometimes  as  salts  of 
various  metals. 

As  salts  of  various  metals  in 
the  cell  sap.  Formed  as  free 
acid  by  the  fermentation  of 
ethyl  alcohol  by  various  bac- 
teria. Produced  in  dry  distil- 
lation of  wood. 

Butyric  (normal)  As  esters  in  various  Apiaceae. 

C4H8O0,  (CH3-CH2-CH.2- 

COOH). 
Isobutyric  Free   in   fruit   of   St.    John's 

[  CHsv  bread  {Ceratonia  siliqua)  and 

C4H8O2,  \  >CH-COOH)in  various  other  plants. 

[  cn/ 

Palmitic,  Stearic   and  Oleic  (see  below  under /«/s). 

Glycollic  In  unripe  fruits  and  leaves  of 

C2H4O3,  (CH2(OH)-COOH)  the  grape. 


Formic 

CH2O2,  (HCOOH) 


Acetic 

C0H4O2,  (CH3COOH) 


ACIDS  AND  ALCOHOLS  141 

Lactic  Formed  by  the  bacterial  fer- 

C^HfiOs  (CH3-CH(0H)  -        mentation  of  milk  sugar  (lac- 
COOH)  tose),    also   by   bacterial   fer- 

mentation in  sauer  kraut  and 
ensilage. 
Oxalic  Free  or  as  acid  or  neutral  salts 

C2H..04(COOH-COOH)         of  Ca,   K   or  Na  in  Oxalis, 

Rumex,   Rheum,   etc.      Very 
abundant  as  Ca  salt  in  the 
form  of  crystals. 
Succinic  In     green     grapes,     and     in 

C4H6O4  (COOH  — CH2  — CH2  various  Papaveraceae  and  As- 
-COOH)  terales. 

Dextro-tartaric  Free  and  as  acid  salt  of  K  in 

C4H606(COOH-CH(OH)-  fruit  of  grapes  and  in  other 
CH(OH)-COOH)  fruits. 

Malic  Very    widely    distributed    as 

C4H6O5  (COOH-CH2-CH-   free  acid  in  fruits,  e.g.  apple, 
(OH)— COOH)  barberry,  grape;  in  leaves  of 

Crassulaceae,  etc. 
Citric  Free     in     fruits     of  Citrus 

C6H807(CH..(COOH)-C-       (orange,  lemon,  etc.),  goose- 
(0H)(C00H)-CH2(C00H))  berry,  etc. 
Benzoic  In  fruit  of  cranberry  and  in 

CtHoO.  (C6H5(C00H))  various  gums. 

Salicylic  In  flowers  of  Ulmaria  and  as 

CtHsOs  (C6H4(0H)(C00H))    an  ester  in  Wintergreen. 
Gallic  In  insect  galls,  tea,  etc. 

C7H6O5  (Cr,H.(0H)3(C00H)) 
Gallotannic  (tannin)  In  great  abundance  in  many 

C14H10O9  (=  two  molecules  of  i)lants;  the  chief  tanning  sub- 
gallic  acid  united,  less  H2O)     stance. 
Alcohols. 

Methvl  As   an   ester   in   some  fruits; 

CH4O  (CH3(0H))  i)roduced  by  dry  distillation  of 

wood. 
Ethyl  Produced    in    the    anaerobic 

C2H6O  (CHa  -CH.,(OII))         stage  of  respiration  of  glucose. 

The  chief  product  (together 
with  CO2)  of  fermentation  of 
glucose  by  yeasts. 


142 


THE  CHEMISTRY  OF  THE  PLANT 


Higher  Alcohols. 


These  are  grouped  under  the 
name  "fusel  oil"  and  are  pro- 
duced in  small  quantities  dur- 
ing the  fermentation  processes 
that  lead  to  the  production  of 
ethyl  alcohol.  The  commonest 
are  the  following. 


Normal  propyl 

CsHsO,  (CH3-CH2-CH2- 

(OH)) 
Normal  butyl 

C4H10O,  (CH3-CH2-CH2 

CH2(0H)) 
Isobutyl       f  CH3\ 

C4H10O,  i 

[  CH3' 

Isobutyl  carbinol 

[  CH, 

C6H12O,  \ 

[CHa/ 
Glycerine 

C3H8O3,  (CHo(OH)-CH- 

(0H)-CH2(0H)) 
Mannite 

CeHuOe,  (CH2(0H)-CH- 

(OH)  -CH(OH)  -CH(OH) 

-CH(0H)-CH20H) 
Dulcite   (formula  as  for  man- 
nite). 
Sorbite  (formula  as  for  mannite) 
Perseite 

CyHieOy,  (CH2(0H)  -  (CH- 

(OH))5-CH2(OH)) 
Fats  and  Fatty  Oils. 


>CH-CH2(0H)) 

Also  found 
mile  oil. 
>CH-CH2-CH2(OH)) 


in  Roman  camo- 


See  under /a/s,  below. 


In  leaves  of  hlac  and  celery, 

in  sugar  cane,  especially  in  the 

manna   ash    {Fraxinus  ornus) 

and  in  many  fungi. 

In  Euonymus,  Melampyrum, 

etc. 

In  service  berries. 

In  seeds  of  the  avocado, 

{Per sea  gratissima) . 

These  are  distinguished  read- 
ily from  the  so-called  ethereal 
or  aromatic  oils  in  that  the 
former  leave  grease  spots  on 
paper  while  the  spots  formed 
by  the  latter  disappear  on 
evaporation.  The  chief  fats 
and  fatty  oils  are  esters  of  the 


FATS  AND  OILS 


143 


Fats  and  Fatty  Oils. — Con. 


Palmitic  acid 

Cl6H3202,(Cl5H31-COOH) 

Stearic  acid 

C18H36O2,  (C17H35-COOH) 
Oleic  acid 

Ci8H3402,(Ci7H33-COOH) 

Ricinoleic  acid 

C18H34O3 
Linoleic  acid 

C18H32O2 
Crotonic  acids 

C4H6O2 

Aromatic  Oils  and  Camphors. 


alcohol  glycerine  and  various 
fatty  acids.  They  are  mostly 
liquid  (i.e.  oils)  in  plants  but 
in  some  tropical  plants  are 
solid  at  ordinary  temperatures. 
Usually  they  are  mixtures  of 
several  fats,  the  three  most 
common  ones  being  the  same 
as  the  commonest  animal  fats, 
viz.:  the  first  three  named 
below.  Upon  the  propor- 
tions of  the  three  depends 
whether  the  fat  will  be  solid  or 
Hquid.  The  acids  concerned 
are: 

Forming     with    glycerine     a 
solid  fat,  palmitin. 
Forming     with    glycerine     a 
solid  fat,  stearin. 
Forming     with    glycerine     a 
liquid  oil,  olein. 
Forming     with    glycerine     a 
liquid  oil  (castor  oil). 
Forming     with    glycerine     a 
liquid  oil  (in  linseed  oil). 
Of  which  several  isomeres  are 
known,  are  found  in  their  glyc- 
erine esters  in  croton  oil. 
These  are  oily  hquids  or  crys- 
talline   solids,    mostly    "ben- 
zene   derivatives,"    occurring 
in  fruits,  leaves  and  stems  of 
many  plants.    The  oily  spots 
made  by  the  oils  disappear  on 
evaporation.    Very  many  are 
known  but  in  many  cases  the 
composition    is    not    satisfac- 
torily worked  out.  Chemically 
they  are  verj^  variable.   Those 
mentioned  below  arc  all  very 
closely  related  to  each  other. 


144 


THE  CHEMISTRY  OF  THE  PLANT 


Pineiic 

C10H16 
d-Limonene 
CioHie 


Cineol  (Eucalvi)tol) 

CioH.sO 
Liiialool 

CioHisO 
Citral 

CioHieO 
Tanacetone 

CioHieO 
Camphor 

CioHieO 
Menthol 

CioHjoO 
Caoutchouc 

(CioHi6)n 

Gutta  Percha 

(CioHi60)n 

Carbohydrates. 


Chief  constituent  of  turpen- 
tine. 

The   chief  oil   of   the  orange 
rind,  also  of  oil  of  dill,  oil  of 
erigeron.     Together  with  pi- 
nene  it  forms  oil  of  citron. 
In  oil  of  luicalyptus. 

In  oils  of  lavender  and  gera- 
nium. 
In  oil  of  bergamot. 

In  oil  of  tans}'. 

In  all  parts  of  the  camphor 
tree. 

Chief  constituent  of  oil  of 
peppermint. 

Produced  in  the  latex  of  many 
plants,  especially  Apocynaceae 
and  Euphorbiaceae. 
In  the  latex  of  Isonamha 
gutta  and  many  other  Sapo- 
taceae. 

The  compounds  grouped 
under  this  head  are  in  their 
nature  in  some  cases  alde- 
hydes, in  others  ketones.  They 
may  be  combined  into  more 
complex  anhydrides  or  ethe- 
real derivatives.  They  con- 
sist of  carbon,  hydrogen  and 
oxygen  in  the  proportion 
CxH2yOy  in  which  x  and  y 
may  be  equal,  or  y  may  be  one 
or  more  less  than  x  (e.g. 
CeHi.Oe,  C12H22O11,  etc.). 
Mostly  x  =  6  or  a  multiple  of 
G.  The  forms  with  low  value 
for  X  (5  or  6  or  12)  are  soluble 
in   water   and   sweet   to   the 


CARBOHYDRATES 


145 


Carbohydrates. — Con. 


Monosaccharids. 

Arabinose 

C5H10O5,  (CH2(0H)-(CH- 

(0H))3-CH0) 
d-Glucose    (grape    sugar,    dex- 
trose) 

CeHioOe,  (CH2(0H)-(CH- 

(0H))4-CH0) 


d-Galactose  (formula  as  for  glu- 
cose) 


d-AIaniiose  (formula  as  for  glu- 
cose) 


d- Fructose  (fruit  sugar  or  levu- 
lose) 
CfiHioO,;,  (CH,(0P^)-(CH- 
(0H))3-C0-CHo(0H)) 
10 


taste  and  dialyze  easil}'.  The 
solubility  and  sweetness  as 
well  as  i)ower  to  dialyze 
decrease  as  the  numl^er  of  car- 
bon atoms  increases.  Those 
with  Ce  (or  C5)  are  called 
monosaccharids;  with  C12,  di- 
saccharids  or  bioses;  Cis,  tri- 
saccharids  or  trioses;  C24, 
tetrasaccharids  or  tetroses; 
those  with  larger  value  of  car- 
bon are  often  termed  poly- 
saccharids.  They  usually  have 
the  formula  (C6Hio05)n. 
Only  the  commoner  forms 
will  be  mentioned. 
Obtained  by  treatment  of 
various  gums  with  dilute 
boiling  H2SO4. 

This  is  the  commonest  sugar. 
It  is  in  most  cases  the  first  car- 
bohydrate produced  in  pho- 
tosynthesis. It  occurs  alDun- 
dantly  in  most  sweet  fruits. 
It  is  the  form  in  which  carbo- 
hydrates are  translocated. 
Produced  b}^  the  splitting  of 
the  lactose,  raffinose,  or  man- 
neotetrose  molecule  by  weak 
acids,  therefore  one  of  the 
constituents  of  these  sugars. 
Produced  by  the  splitting  of 
the  molecule  of  certain  (re- 
serve) celluloses  by  weak  acida 
and  therefore  one  of  the  con- 
stituents of  those  carbohy- 
drates. 

This    sugar    is    abundant    in 
many  sweet  fruits,  e.g.  graj)e. 


146 


THE  CHEMISTRY  OF  THE  PLANT 


Sorbinose      (formula 

d-fructosc) 
Disaccharids. 


Saccharose  (Cane  sugar) 
d-glucose  -f  d-f  ructose 


Trehalose  (Fungus  sugar) 
d-glucose + d-glucose 

Maltose  (Malt  sugar) 
d-glucose + d-glucose 

Lactose  (Milk  sugar) 
d-glucose + d-galactose 

Trisaccharids. 


Raffinose 

d-f  ructose + d-galactose + d- 

fructose 
Tetrasaccharids. 


Manneotetrose 

C24H44O22,  d-f  ructose  H-d- 
glucose + d-galactose + d- 
galactose. 


as     for  In  juice  of  the  fruit  of  the 
service-berr}'. 

These  are  to  be  looked  upon  as 
formed  by  the  union  of  two 
(not  necessarily  similar)  mole- 
cules of  monosaccharids  with 
the  loss  of  H2O.  Their  arbi- 
trary formula  is  C12H22O11. 
The  exact  arrangement  of  the 
groups  within  the  molecule  is 
still  disputed,  so  that  no  at- 
tempt will  be  made  to  show 
it.  The  component  monosac- 
charids are  given  in  each  case. 
Very  abundant  in  the  higher 
groups  of  plants  in  stems, 
roots  and  fruits.  Found  in 
sugar  beet,  sugar  cane,  Indian 
corn,  maple,  birch,  and  various 
palms,  etc. 
Abundant  in  fungi. 


In  germinating  starchy  seeds. 

Common    in    milk    but    only 
rarel}'  in  plants. 
These  have  the  arbitrary  for- 
mula C18H32O16  and  are  looked 
upon  as  composed    of   three 
monosaccharid     molecules 
joined  with  the  loss  of  2H2O. 
Occurs    in    the    sugar    beet 
(abundant  in  beet  molasses), 
cotton  seeds,  etc. 
These    are    formed    by    the 
union  of  four  monosaccharids 
with  loss  of  water. 
In   gum   of   the   Manna   ash 
(^Fraxinus  ornus). 


CARBOHYDRATES 


147 


Polysaccharids. 


Starch  (Amylum). 


Glycogen  (Liver  starch) 


InuHii 


Celluloses 


The  following  carbohydrates 
have  an  arbitrary  formula 
corresponding  nearly  if  not 
exactly  to  (CeHioOs),.  in 
which  n  may  be  different  for 
the  different  forms.  They 
are  looked  upon  as  composed 
of  n  molecules  of  monosac- 
charids  with  loss  of  some 
H2O.  They  are  mostly  little  if 
at  all  soluble  in  water  and  are 
correspondingly  lacking  in 
sweetness.  They  are  the  com- 
monest forms  of  reserve  car- 
bohydrates. 

Hydrolyzes  ultimately  to  d- 
glucose.  The  commonest  form 
of  reserve  carbohydrate  for 
green  plants.  Always  pro- 
duced in  plastids  (chloroplasts 
or  leucoplasts).  Usually 
formed  in  grains  of  alternating 
denser  and  less  dense  concen- 
tric la3^ers.  Occurs  in  many 
modifications  (i.e.  there  are 
many  starches). 
Hydrolyzes  to  d-glucose. 
Very  abundant  in  fungi.  Is 
the  storage  carbohydrate  of 
animals  also. 

Hydrolyzes  to  d-g  1  u  c  o  s  e. 
Stored  in  solution  in  roots  and 
tubers  of  Asterales  (e.g.  Dah- 
lia). 

These  are  water-insoluble 
compounds  which  form  the  cell 
walls  of  most  plants.  Many 
forms  have  been  distin- 
guished, differing  in  their  solu- 
bility   in    weak     acids    and 


1-18 


THE  CHEMISTRY  OF  THE  PLANT 


Glucosides. 


Amygdalin 
C20H27NO11 


Solanin 
C28H47NOU 

Saponin 

C32H52O17 
Coniferin 

CifiHo^Os 


alkalies  and  in  the  form  of 
monosaccharids  produced  on 
hydrolysis.  We  can  distin- 
guish the  celluloses  proper  (in- 
soluble in  weak  acids  and 
alkalies,  but  soluble  in  am- 
moniacal  copper  oxide  solution 
and  hydrolyzing  with  diffi- 
culty) and  the  hemi-celluloses 
(reserve  celluloses  are  of  this 
type),  pectoses,  etc.,  with  all 
gradations  to  the  plant  gums 
which  are  pectic  in  nature  and 
soluble  in  water. 
These  are  compounds  of  glu- 
cose with  various  other,  often 
not.  closely  related,  substances 
from  which  the  glucose  is  set 
free  by  the  action  of  enzymes 
or  acids.  The  most  important 
are: 

This  occurs  in  the  leaves,  bark 
and  kernels  of  peach,  bitter  al- 
mond, cherry,  etc.  Under  the 
influence  of  the  enzyme  emul- 
sin  it  breaks  up  into  d-glu- 
cose,  oil  of  bitter  almonds 
(CeHs-CHO)  and  hydrocy- 
anic acid  (HCN). 
In  green  portions  and  seeds  of 
the  potato  and  other  Solana- 
ceae. 

In  soap  bark  (Sapindus)  and 
many  other  plants. 
In   young   wood   of   Conifers 
(see  below  under  hadromal  for 
discussion). 


GLUCOSIDES  AND  ALKALOIDS 


149 


Hesperidin 

CooH^fiOi, 
Aesculin 

C15H16O9 
Arbutin 

C12H16O7 
Salicin 

CuHigOr 
Alkaloids. 


Caffeine  (Theine) 
C8H10N4O2 

Theobromine 

Piperin 

CiyHiglSOa 

Abrotanin 
C21H00X2O 

Aconitin 
C33H45NO12 


In  green  oranges. 

In    bark   of    horse    chestnut 

(Aescukis). 

In  leaves  of  bear})erry  (Arcto- 

staphylos) . 

In  the  willow. 

These  are  organic  compounds, 
acting  as  bases  in  the  presence 
of  acids,  and  usually  bitter  to 
the  taste.  Under  this  name 
are  grouped  a  variety  of  un- 
related substances  although 
the  tendency  now  is  to  limit 
the  name  to  derivatives  of  the 
pyridin  group  which  would 
exclude  the  first  two  in  the  list 
below  of  the  commoner  alka- 
loids. Many  if  not  most 
alkaloids  are  poisonous.  They 
may  be  in  some  cases  reserve 
foods  but  possibly  in  other 
cases  are  waste  products  or 
even  special  defences  against 
herbivorous  animals. 
In  leaves  of  tea,  "berries"  of 
coffee  and  in  many  other 
plants  (e.g.  Cola  nut). 
In  seeds  of  the  cacao. 

In  pepper  {Piper  nigrum). 

In      wormwood       (Artemisia 

ahrotanum). 

In   monkshood  (Aconitum). 


150 


THE  CHEMISTRY  OF  THE  PLANT 


Atropine 

C17H23NO3 
Berberin 

C20H17NO4 
Brucine 

C23H26N:!04 

Cocaine 

C17H21NO4 
Coniine 

CsHnN 

Cytisin 
C11H14N2O 


Hydrochinin 
C20H26N2O2 

Hyoscyamine 
C17H23NO3 

Lupinin 
C10H19NO 

Morphine 

CiyHiglsOa 

Nicotine 

C10H14N2 
Quinine 

C20H30N  2O2 
Strychnine 

G21H22N  2O2 
Taxin 

C37H52NO10 

Veratrine 

C22H42NO9 
Protein  Group. 


In  leaves  of  Atropa  bella- 
donna. 

In    Berberidaceae,  Ranuncu- 
laceae,  Papaveraceae,  etc. 
In  the  seeds  of  nux  vomica 
{Strychnos  nux-vomica. ) 
In  leaves  of   coca  (Erythrox- 
ylon  coca) . 

The  poisonous  principle  of  the 
hemlock  {Coniiim  macula- 
turn). 

In    various     Fabaceae,    e.g. 
Cytisus,  Laburnum,  Sophora, 
Thermopsis,    Baptisia,    Ulex, 
etc. 
In  Cinchona  bark. 

I  n      henbane      {Hyoscyamus 

niger). 

In  seeds  of  various  lupines. 

The  chief  of  many  alkaloids 
in  opium,  the  coagulated  latex 
of  Papaver  somniferum. 
In  tobacco. 

In  the  bark  of  Cinchona. 

In   the  seeds  of   nux  vomica 

{Strychnos  nux-vomica). 

In  twigs,  leaves  and  fruit  of 

the    European    yew    {Taxu^ 

baccata) . 

In  Veratrum  album. 

This  embraces  a  vast  number 
of  very   complex   compounds 


PROTEINS  151 

Protein  Grouv. — Con,  whose  true  composition  is  in 

great  part  not  yet  clear.  They 
contain  C,  H,  0  and  N  in 
fairly  large  amounts  and  usu- 
ally some  S  and  often  P.  They 
may  also  have  in  combination 
certain  metallic  bases,  but 
this  is  not  proved.  They  are 
probably  built  up  of  combined 
chains  of  amino-acids.  Pos- 
sibly hydrocyanic  acid  is  one 
of  the  steps,  for  it  is  abundant 
in  many  plants  when  protein- 
synthesis  is  active.  Possibly 
carbohydrates  also  are  of 
importance  in  the  framework 
of  the  molecule.  The  molecule 
is  very  large  and  in  the  more 
complex  forms  dialysis  does 
not  occur  or  oi\\y  feebly,  but 
in  forms  like  peptones  it 
readily  takes  place.  The  high- 
er forms  lead  to  the  Proto- 
plasms  which  are  chemically 
to  be  regarded  as  very  com- 
plex protein  compounds  in 
which  probabl}'  various  metal- 
lic bases  are  combined  and 
which  perhaps  have  one  or 
more  carbohydrate  nuclei  in 
the  molecule.  They  are  very 
labile  compounds,  easily  de- 
stroyed by  external  influences 
of  varied  nature.  The  proto- 
plasm and  higher  protein 
compounds  {Albinucns)  are 
usually  easily  coagulable  by 
heat  and  by"^salts  of  Cu,  Hg, 
Ag,  etc.  By  hydrolysis  with 
certain  enzymes  these  com- 
pounds are  broken  down  into 


152 


THK  CHEMISTRY  OF  THE  PLANT 


Protein  Group. — Con. 


Enzymes. 


Invertase 
Cytase 


the  less  complex,  soluble,  di- 
alyzable  Albumoses  (to  which 
the  peptones  belong).  Other 
related  groups  are  the  Albu- 
minoidSf  some  of  which  are 
crystallizablc.  All  of  these 
groups  have  innumerable 
forms  differing  from  one 
another  in  solubility  in  acids, 
alkaUes  and  salt  solutions;  in 
their  coagulabihty  with  heat, 
salts,  acids  and  alkalies  and 
enzymes;  in  their  power  to 
dialyze,  and  in  the  forms  of 
enzymes  that  can  attack  them 
and  the  forms  of  the  pro- 
ducts of  such  enzymatic 
action. 

These  are  substances  showing 
many  of  the  characteristics  of 
the  protein  compounds  (e.g. 
destruction  of  activity  by  heat 
or  salts  of  heavy  metals,  etc.), 
but  not  so  complex.  They  are 
very  numerous,  even  in  the 
same  plant,  and  perform  many 
of  its  important  functions. 
They  are  in  a  sense  ''cataly- 
zers," in  that  they  start  or 
intensify  chemical  processes 
without  themselves  being  used 
up  (or  only  in  relatively  small 
degree) . 

The  more  important  plant  en- 
zymes and  the  substances 
acted  upon  by  them  are  as 
follows : 

Hydrolyzing  saccharose  to  d- 
glucose  and  d-fructose. 
Hydrolyzing  hemicelluloses  to 
•  monosaccharids. 


ENZYMES 


l-)3 


Pectase 

Amylase  (diastase) 

Zymase 
Emulsin 

Lipase 

Pepsins  and  trypsines 

Oxidases  and  peroxidases 

Catalase 

Reductase 

Miscellaneous  substances. 


Methane 

CH4 
Heptane 

C7H16 
Methylamine 

CHsX,  (CH3NH2) 
Tri-methjdaminc 

C3H9N,    (CH3)3X) 

Formaldehyde 
CH20,(H-CH0) 


Ilydrolyzinjs;  pectin  com- 
pounds to  monosaccharids. 
Hydrolyzing  starch  to  d-glu- 
cose  (probably  several  steps, 
involving  perhaps  several 
enzymes). 

Sphtting  d-glucose  into  ethyl 
alcohol  and  CO2. 
Hydrolyzing     amygdalin     to 
HCN,    d-glucose   and    oil    of 
bitter  almonds. 
Acting    on    fats,    saponifying 
and  emulsifjang  them. 
Hydrolyzing  protein   com- 
pounds to  different  degrees  of 
simplicity. 

IMany  kinds,  bringing  about 
numerous  oxidations  within 
the  plant. 

Decomposing  peroxides  in  the 
plant. 

Bringing  about  reducing  proc- 
esses in  the  plant. 
Under  this  head  are  grouped  a 
number  of  totall}^  unrelated 
substances  that  do  not  come 
under  anj^  of  the  foregoing 
heads  and  that  are  not  numer- 
ous enough  to  form  classes  by 
themselves. 

Produced  by  bacterial  fermen- 
tations of  celluloses. 
In  the  oil  from  the  seeds  of 
some  pines. 

In  Mercitrialis  pcrcnuis  and 
M.  annua. 

In  Chenopodium,  in  blossoms 
of  Crataegus,  and  of  pear,  etc. 
Apparently  one  of  the  first 
steps  in  the  photosynthesis  of 
CO2  and  HO2  to  form  carbo- 


154 


THE  CHEMISTRY  OF  THE  PLANT 


Formaldehyde — C 


Asparagin 

C4H8N0O3,  (CO(XHo)  -  CH2 
-CH(XHo)-COOH). 


Chit  in 
CisH 


iNoOi 


hydrates.  Found  free  in 
minute  quantities  in  leaves 
when  active  photosynthesis  is 
occurring. 

This  is  found,  especially  in  the 
growing  regions,  in  many 
plants,  e.g.  asparagus,  peas, 
beans,  vetches,  beet  roots, 
potatoes,  etc. 

This  forms  part  of,  or  in  some 
cases  is  the  chief  constituent  of, 
the  cell  wall  of  many  of  the 
lower  plants,  e.g.  Myxo- 
phyceae,  Mucorales,  Carpo- 
myceteae.  It  was  long  con- 
sidered a  form  of  cellulose 
("fungus  cellulose")-  It 
forms  the  body  waU  of  insects, 
crustaceans,  etc. 
Formed  by  the  fermentation 
of  the  seed  pods  (''beans")  of 
the  Vanilla  plant,  whence  it  is 
extracted  by  alcohol.  It  is 
present  in  most  if  not  all 
lignified  cell  walls  and  is 
possibly  one  of  the  substances 
giving  the  cell  wall  the  char- 
acters that  we  call  "lignifica- 
tion"  (see  hadromal). 
Hadromal  (composition  uncer-  This  is  a  substance  separated 
tain)  by  Czapek  from  hgnified  cell 

walls  and  believed  by  him  to 
be  what  gives  them  their 
"Hgnified"  character.  On  the 
other  hand  many  botanists  do 
not  consider  this  as  the  impor- 
tant body  and  ascribe  hgnifi ca- 
tion to  the  presence  in  the  cell 
walls  of  conifcrin  and  vanilhn 
(q.v.)  and  perhaps  other  sub- 
stances. 


Vanillin 
CsHsOa 


PIGMENTS 


155 


Suberiu 


Cutin 


Chlorophyll  (chlorophyllan) 


Carotin  (Xanthophyll) 
C26H38 


This  is  the  name  appHed  to 
what  is  proi)ably  a  mixture  of 
several  fatty  acids  including 
the  following:  Phellonic,  phloe- 
onic  and  suberic  (CgH^Os). 
Their  presence  in  the  cell  walls 
waterproofs  them. 
This  is  a  fatty  substance  or 
substances  related  to  the  fore- 
going and  waterproofing  the 
epidermal  cell  walls  in  which 
it  is  deposited. 

This  is  a  blue-green  pigment 
occurring  only  in  chloroplasts 
(or  in  such  Myxophyceae  as 
lack  definite  chloroplasts  in 
minute  particles  in  the  cyto- 
plasm). It  is  the  most  im- 
portant plant  pigment,  ab- 
sorbing certain  light  rays  and 
transforming  the  energy  into 
the  chemical  energy  used  in 
photosynthesis.  It  is  formed 
(with  rare  exceptions)  only  in 
the  light  and  is  itself  quickly 
destroyed  by  bright  fight.  It 
contains  no  iron  but  the  plant 
requires  iron  for  its  produc- 
tion. Its  chemical  composi- 
tion is  not  exactly  known  but 
it  seems  to  be  closely  related 
to  haemoglobin.  It  is  insoluble 
in  water  but  soluble  in  alcohol, 
ether,  petroleum  ether,  gaso- 
line, etc.  Probably  "chloro- 
j)hyir'  is  not  one  but  a  group 
of  closely  similar  compounds. 
Under  the  name  Xanthoi)hyll 
this  substance  is  associated  in 
small  or  ,largc  proj)ortions 
with  chlo5i)hyll  wlierrever  the 
latter  occurs,  the  mixture  giv- 


156 


THE  CHEMISTRY  OF  THE  PLANT 


ing  the  characteristic  ''grass 
green"  color  to  the  chloro- 
plasts.  It  is  present  without 
chloroph}^!  in  autumn  leaves 
and  in  many  parts  of  some 
plants.  The  autumn  colora- 
tion of  leaves  is  due  to  various 
chemical  changes  of  carotin 
and  chlorophyll  and  other  sub- 
stances present  in  the  cells. 
Carotin  is  of  itself  yellow  to 
orange  when  in  solution,  form- 
ing orange-red  to  red  crystals. 
It  is  insoluble  in  water,  petrol- 
eum ether  and  gasohne,  but 
soluble  in  alcohol,  ether,  etc. 
Other  plant  pigments,  of  un- 
known composition,  may  be 
associated  w4th  the  two  pre- 
ceding pigments,  giving  char- 
atceristic  colors  to  the  chloro- 
plasts.  Their  function  is  not 
proved,  but  in  some  cases  they 
probably  change  the  quality  of 
light  to  that  most  favorable  for 
absorption  by  the  chlorophyll. 

Phycocyanin  In    the    Myxophyceae,  blue, 

water  soluble. 

Phycophaein  In  the  Phaeophyceae,  brown. 

Diatomin  In    Bacillarioideae   (diatoms) 

brown,  water  soluble. 

Phycoerythrin  In  Rhodophyceae  and  a  few 

Siphonophyceae,  violet-red, 
water  soluble. 

Anthocyanin  is  a  red  (in  acid  cell  sap)  or  blue  (in  alkaline  cell 

sap)  coloring  matter  in  the 
cell  sap  of  many  brightly 
colored  leaves  and  other  plant 
parts,  occurring  especially  in 
the  epidermal  cells.  It  is  ap- 
parently a  nitrogen-free  glu- 
coside. 


CHAPTER  VI 
THE  CLASSIFICATION  OF  PLANTS 

202.  We  now  come  to  that  part  of  the  subject  in  which 
we  are  to  consider  the  different  kinds  of  plants  to  be 
found  in  the  world.  Botanists  now  know  over  233,000 
kinds,  a  number  which  is  too  vast  to  be  remembered  in 
detail  by  any  one  and  yet  even  the  beginner  may  learn 
much  about  them  by  taking  up  their  study  properly. 

Of  Relationship 

203.  It  is  now  known  that  all  the  kinds  of  plants  are 
related  to  one  another.  By  this  we  mean  that  traced 
back  far  enough  all  plants  have  a  common  ancestry,  in 
other  words  they  have  descended  from  earlier  identical 
or  similar  forms.  This  is  what  we  know  as  Evolution, 
and  in  thinking  of  the  great  numbers  of  plants  we  regard 
them  as  related  to  one  another  because  they  have 
descended  recenth'  or  remotely  from  common  ancestors. 

204.  In  Botany  we  try  to  group  plants  according  to 
their  relationships,  much  as  we  group  people  by  their 
relationships.  This  requires  that  as  we  study  plants  we 
should  constantly  keep  in  mind  the  fact  that  they  are 
less  or  more  alike  just  as  their  relationship  is  remoter  or 
nearer.  And  this  is  what  we  call  Phylogeny,  that  is,  the 
racial  history  of  the  groups  of  plants.  So  what  follows 
in  Chapters  VII  to  XX  is  an  attempt  to  present  selected 
representatives  of  the  groups  of  plants  in  such  a  sequence 
as  will  suggest  their  relationship  and  path  of  development. 

205.  It  must  be  remembered  that  plants  have  been  in 
existence  for  a  very  long  time,  and  that  many,  or  possi- 

157 


158  THE  CLASSIFICATION  OF  PLANTS 

bly  all  of  the  earliest  kinds  have  disappeared.  If  we 
had  before  us  all  of  the  plants  that  ever  existed  the  task 
of  arranging  them  so  as  to  show  their  relationship  would 
still  be  a  difficult  one,  but  with  many  forms  irretrievably 
lost  the  difficulty  of  the  task  is  very  greatly  increased. 
Some  lower  plants  are  probably  still  much  like  their 
primitive  ancestors,  while  others  have  been  greatly 
modified.  We  may  think  of  the  plants  that  we  now  see 
as  having  developed  through  shorter  or  longer  distances; 
some  perhaps  have  stood  still  in  their  original  places, 
others  have  moved  forward  short  distances  to  where  we 
now  find  them,  while  still  others  have  gone  much  farther 
along  their  evolutionary  pathway  to  their  present 
positions. 

Of  Species  and  Genera 

206.  In  studying  plants  we  notice  that  they  exist  as 
kinds,  and  there  has  been  a  general  agreement  to  speak  of 
each  recognizable  kind  as  a  "species."  Thus  we  speak 
of  the  species  of  Oaks,  Elms,  Ashes,  Magnolias,  etc., 
meaning  the  kinds  of  Oaks  (White  Oak,  Red  Oak,  Black 
Oak,  etc.),  or  Elms  (White  Elm,  Sfippery  Elm,  Cork  Elm, 
etc.),  or  Ash  (White  Ash,  Green  Ash,  Black  Ash,  etc.), 
etc.,  etc.,  and  in  all  these  cases  we  recognize  that  we  refer 
to  a  quite  definite  kind — a  species.  While  in  many  cases 
the  distinctions  are  less  definite,  it  is  still  true  that  in  any 
particular  locality  plants  are  recognizable  as  kinds 
(species).  Now  these  species  are  sufficiently  stable  so 
that  under  constant  conditions,  in  any  particular  locality 
they  change  slowly,  if  at  all,  while  they  are  sufficiently 
plastic  so  that  under  changed  conditions,  as  when  they 
are  carried  to  other  habitats,  they  change  more  or  less, 
and  this  may  be  great  enough  so  that  we  regard  them  as 
different  species. 


HIGHER  GROUPS  159 

207.  For  our  own  convenience  we  group  similar  species 
into  genera.  Thus  we  group  all  the  species  of  oaks  into 
one  genus  Quercus,  the  old  Latin  name  for  all  the  Oaks, 
and  in  like  manner  all  the  Elms  are  grouped  under  U Imus, 
the  Latin  name  for  the  Elms.  So  we  have  Quercus  alba, 
Quercus  rubra,  Quercus  nigra,  etc.,  and  Ulmus  americana, 
Uhnus  fulva,  Ulmus  racemosa,  etc.,  in  all  of  which  cases 
the  first  name  is  that  of  the  genus,  and  the  second  that  of 
the  species  and  these  constitute  the  names  of  these  plants. 
The  name  of  the  plant  comes  thus  from  its  classification. 

Higher  Groups 

208.  For  further  convenience  all  genera  are  gathered 
into  their  appropriate  families,  all  famihes  into  orders,  all 
orders  into  classes,  and  finally  all  classes  into  phyla. 
Lastly  all  the  kinds  of  plants  in  the  world  are  said  to  con- 
stitute the  Vegetable  Kingdom. 

We  may  arrange  these  as  follows: 
Species  consist  of  individual  plants 
Genera  are  composed  of  species 
Families  are  collections  of  genera 
Orders  are  collections  of  families 
Classes  are  collections  of  orders 
Phyla  are  collections  of  classes 

The  vegetable  kingdom  is  a  collection 
of  phyla. 
From  this  it  follows  that: 

Every  plant  belongs  to  some  species 
Every  species  to  some  genus 
Every  genus  to  some  family 
Every  family  to  some  order 
Every  order  to  some  class 
Every  class  to  some  phylum 

All  phyla  to  the  Vegetal)lc  Kingdom. 


160  THE  CLASSIFICATION  OF  PLANTS 

So  the  Vegetable  Kingdom  contains 
Phyla 

Classes  (also  Sub-classes) 

Orders  (also  Super-orders,  and   Sub-orders) 
Families  (also  Sub-families) 
Genera 
Species. 

The  foregoing  may  be  called  the  framework  of  the 
classification  of  plants  used  in  this  book. 

209,  It  must  be  borne  in  mind  that  in  this  classification 
we  are  dealing  with  individuals  as  the  only  actually  ex- 
istent things.  For  our  own  convenience  we  form  a 
mental  concept  of  an  aggregation  of  similar  individuals, 
and  this  we  hold  as  "kind"  ('' species")-  So  also  we 
form  a  mental  picture  of  an  aggregation  of  similar  species, 
and  this  is  what  we  call  the  genus.  Quite  similarly  we 
form  a  concept  of  aggregated  genera,  and  call  it  a  family, 
and  so  on  for  orders,  classes  and  phyla. 

Evolution 

210.  For  the  present  purpose  the  more  important 
points  included  in  the  general  doctrine  of  evolution  may 
be  summarily  stated  as  follows: 

1.  The  first  species  were  lower  plants,  and  these  gave 
rise  to  higher  plants. 

2.  Evolution  while  generally  upward  (progressive)  is 
often  downward  (retrogressive). 

3.  Evolution  does  not  necessarily  involve  all  organs  of 
the  plant  equally  in  any  particular  period,  and  one  organ 
may  be  progressing  at  the  same  time  that  another  is 
retrograding. 

4.  Hysterophytic  retrogression  of  plants  is  persistent, 
and  the  hysterophytic  phylum  does  not  afterward  be- 
come holophytic. 


EVOLUTION  101 

5.  All  plant  relationships  are  genetic,  and  these  rela- 
tionships are  up  and  doini  the  genetic  Hnes. 

Origin  of  Phyla 

211.  If  now  we  inquire  as  to  the  origin  of  phyla  we  may 
formulate  our  answer  in  several  ways.  Stated  philo- 
sophically we  may  say  that  a  phylum  originates  with 
the  incoming  of  a  new  idea.  Stated  structurally,  it  has 
its  beginning  with  the  development  of  a  dominant  mor- 
phological peculiarity.  Stated  taxonomically,  its  initial 
point  is  indicated  bj^  the  appearance  of  a  new  character. 
So  every  phylum  is  the  result  of  a  development  which 
differs  from  that  which  preceded  it  because  of  the  incom- 
ing of  a  new  idea:  this  dominant  idea  was  manifestetl 
structurally  by  a  divergence  from  the  previous  lines  of 
evolution  and  this  point  of  divergence  became  the  actual 
origin  of  the  new  phylum.  As  long  as  this  idea  and  its 
structural  expression  dominate,  so  long  does  the  phylum 
extend,  and  when  a  still  newer  idea  comes  in  and  attains 
dominance,  a  still  newer  phylum  has  its  beginning.  So 
we  say  that  a  phylum  originates  with  a  divergence  which 
is  the  expression  of  a  new  idea,  or  in  other  words  a  ''tend- 
ency"; and  this  in  taxonomy  we  call  a  ''new  character." 

The  Place  of  Plants  in  Time 

212.  As  stated  a])ove,  plants  have  been  in  existence  a 
ver}'  long  time,  and  as  some  references  will  be  made  in  the 
following  chapters  to  particular  periods  of  time  it  is 
necessary  here  to  give  a  table  showing  the  divisions  of 
earth  time  (''geologic  time")  as  recognized  in  recent 
treatises,  with  suggestions  as  to  their  vegetation.  In  this 
table  no  attempt  is  made  to  indicate  the  relative  lengths 
of  different  periods. 

11 


162 


THE  CLASSIFICATION  OF  PLANTS 


General  Table  of  Geologic  Time  Divisions 


Cexozoic 
(Tertiary) 


Mesozoic  , 


Paleozoic, 


Proterozoic. 
Archeozoic. 


Present — All  i^hyla  including  highest  Flow- 
ering Plants. 

Pleistocene — Nearly  as  at  present. 

Pliocene     1 

Miocene      [  Increase    in    higher    Flowering 

Oligocene  J       Plants. 

Eocene — Increase  of  Flowering  Plants. 

Upper  Cretaceous — Rapid  increase  of  lower 
Flowering  Plants. 

Lower  Cretaceous  (Comanche  or  Shastan)  — 
Appearance  of  lower  Flowering  Plants. 

Jurassic — Ferns,  Cycads,  Conife^^. 

Triassic — Ferns,  Cycads,  Conifers. 

Permian — Ferns,  Calamites,  Lycopods,  Cy- 
cads, Conifers. 

Coal  Measures,  or  Pennsylvanian — Ferns, 
Calamites,  Lycopods,  Cycads. 

Subcarboniferous,  or  Mississippian —  Ferns, 
Calamites,  Lycopods,  Cy'cads. 

Devonian — Ferns,  Calamites,  Lycopods,  Cy- 
cads. 

Silurian — Probably  some  land  vegetation. 

Ordovician — Probabty  some  land  vegetation. 

Cambrian — Apparently  some  higher  algae. 

Keweenawan  1  Probably 

Animikean  (Upper  Huronian)  >  only  simple 

Huronian  J      algae. 

Archean  Complex — Probably  only  very  sim- 
ple algae. 


CHAPTER  VII 

PHYLUM  I.     MYXOPHYCEAE 
THE  SLIME  ALGAE 

213.  The  Slime  Algae  are  the  lowest  and  simplest 
plants,  and  are  often  so  minute  as  to  require  the  highest 
powers  of  the  microscope  for  their  study.  Some  of  them 
are  single  cells,  while  others  are  rows  or  masses  of  similar 
or  slightly  different  cells.  In  most  Slime  Algae  the  cells 
are  poorly  developed,  the  walls  being  soft  and  easily 
gelatinized  and  usually  containing  chitin,  the  nuclear 
matter  diffused  and  not  bounded  by  a  nuclear  membrane, 
and  the  cytoplasm  containing  no  plastids. 

214.  The  dominant  coloring  matter  of  the  cells,  phiy- 
cocyanin,  which  is  blue,  is  mostly  distributed  through- 
out the  protoplasm,  and  mixed  with  the  chlorophyll  and 
more  or  less  carotin  give  the  blue-green,  brown-green, 
or  smok}^  color  found  in  this  group.  In  the  hystero- 
phytes  these  are  wanting. 

215.  They   reproduce    asexually   by    fission, 
and  the  formation  of  spores,  and  in  the  fila- 
mentous forms  by  the  breaking  of  the  filaments 
into    short    segments    (hormogones)    each    of   fig.  59. 
which   then  grows  into   a  long  filament.     No   theMyxo- 
sexual  reproduction  is  known.  ^  ^^*^^^" 

216.  The  Slime  Algae  mostly  live  in  the  water,  getting 
their  nourishment  from  the  solutions  it  contains.  The 
green  plants  (holophytes)  are  able  to  use  carbon  dioxide, 
but  those  not  green  (hysterophytes)  are  typically  par- 
asitic or  saprophytic. 

163 


164  PHYLUiM  I.     MYXOPHYCEAE 

217.  In  this  Pln^lum  the  dominant  idea  is  the  simple 
nucleus,  typically  not  limited  by  a  nuclear  membrane, 
asexual  reproduction,  and  blue-green  color. 

There  are  two  classes: 

I.  Nucleus  not  definitely  outlined,  no  nuclear  membrane;  no 
plastids.  Class  1.  Archiplastideae. 

II.  Nucleus  definitely  outlined,  with  a  nuclear  membrane; 
plastids  present.  Class  2.  Holoplastideae. 


Class  1.  ARCHIPLASTIDEAE  (CYANOPHYCEAE) 
The  Blue  Greens 

218.  In  these  plants  (numbering  about  2000  species) 
there  is  no  limiting  membrane  around  the  primitive 
nucleus,  and  yet  there  is  a  simple  karyokinetic  process 
in  cell  division.  In  the  absence  of  plastids  the  coloring 
matter  is  diffused  throughout  the  cell. 

ORDER  COCCOGONALES.    Unicellular  Blue  Greens 

219.  Here  the  plants  are  strictly  unicellular,  although 
they  may  be  aggregated  into  colonies  in  which  the  cells 
are  included  in  a  gelatinous  matrix  due  to  the  softeuing 
of  their  walls. 

220.  These  are  the  lowest  and  simplest  of  plants;  they 
<-s /TN  live  as  single  cells  in  the  water,  or  they  may 
©Q    ^       ^^6   aggregated  into  slimy  films  on  sticks 

§and  stones.     The  principal  family  is  Chro- 
ococcaceae,   represented  by  minute  species 
Fig.   go  —  of  Chroococcus,  Gloeocapsa,  Aphanocapsa, 
chrooV^)?Jurand  Mcrismopcdia  and  other  genera.    Each  cell 
Gloeocapsa.  dividcs  iuto  two,   and   these  soon  divide 

again,  and  so  on.  In  Merismopedia  the  successive 
divisions  are  in  two  planes,  resulting  in  quadrate 
colonies  of  regularly  arranged   cells. 


FILAMENTOUS  BLUE  GREENS  Kio 

ORDER   HORMOGONALES.    Filamentous  Blue  Greens 

221.  These  plants  consist  of  simple  or  branched  rows 
(filaments)  of  cells,  which  are  usually  enclosed  in  a 
sheath.  There  are  half  a  dozen  families,  the  lowest  of 
which  is  Oscillator iaceae,  with  cylindrical  filaments  of 
uniform  cells.  There  are  many  genera,  as  Microcolcus, 
L3'ngb3"a,  Spirulina,  Oscillatoria,  etc.,  which  occur  in 
quiet  waters.  Oscillatoria  and  Spirulina  are  interesting 
because  of  their  marked  motility. 

222.  The  Nostocs  (Family  Nostocaceae)  are  filamen- 
tous with  more  or  less  spherical  cells,  some  of  which 
are  larger  (rarely  smaller)  than  the  others  and  have 
thickened,  cellulose  walls  (heterocysts).  Spores  are 
common  as  larger,  denser  cells  which  serve  to  carry  the 
species  through  adverse  conditions.  The  genera  Nostoc, 
Anabaena,  and  Cyhndrospermum  are  common. 


^m^^^^nnlt.Hltf]^ 

Fig.     61. — Oscilla-  Fig.  62. — Scytonema  and 

toria  and  Nostoc.  Rivularia. 

223.  The  Scytonemas  (Family  Scytonemataceae)  have 
cylindrical  (often  branched)  filaments  which  contain 
heterocysts  also.  Scytonema  and  Tolypothrix  are 
common  genera. 

224.  The  Rivularias  (Famil}^  Rividar iaceae)  are  taper- 
ing filaments  with  a  heterocyst  at  the  base.  They 
usually  occur  in  jelly-like  masses.  The  principal  genus 
is  Rivularia. 

225.  The  Stigonemas  (Family  Stigoncmataccac),  while 
filamentous,  have  their  larger  filaments  composed  of  more 
than  one  row  of  cells.  Haplosiphon  and  Stigonema  are 
common  genera. 


166  PHYLUM  I.     MYXOPHYCEAE 

ORDER  BACTERIALES.    The  Bactkria 

226.  Tli(^  Bacteria,  wliich  are  here  regarded  as  degen- 
erated chlorophyll-less  Blue  Greens,  are  so  important 
that  they  require  a  somewhat  fuller  treatment.  They 
are  the  smallest  of  living  things,  some  being  as  small  as 
0.0005  millimeters  (1/50,000  inch),  or  even  smaller.  Al- 
though typically  filamentous  they  break  up  easily  into 
one-celled  or  few-celled  forms,  in  which  condition  they 
are  most  commonly  found.  In  some  species  they  occur 
as  minute  rounded  cells  (''cocci"),  in  others  elongated 
(then  called  ''rods"),  and  in  still  others  they  are  more  or 
less  curved.  They  are  frequently  provided  with  one  or 
more  cilia  or  flagella  by  means  of  wdiich  they  are  motile. 

227.  Bacteria  are  found  in  great  numbers  in  the  watery 
parts  of  decaying  organic  matter,  causing  various  kinds 

of  fermentation,  and  in  fact  they  occur  so 
generally  in  Nature  that  their  presence  is 
almost  universal.  They  reproduce  by  fis- 
sion with  such  astonishing  rapidity  that  in 
^^°"b!fct7r?a.' """^^^  a  short  time  they  swarm  in  any  exposed 
substance  which  is  capable  of  furnishing 
them  with  food.  Some  of  the  species  live  in  the 
watery  juices  of  plants  and  animals,  causing  various 
diseases.  However,  of  the  hundreds  of  species  known, 
the  great  majority  are  harmless,  or  actually  beneficent. 

228.  Some  bacteria  can  endure  high  temperatures, 
especially  in  the  spore  state,  and  frequently  appear  in 
tightly  closed  vessels  whose  contents  have  been  boiled. 
Some  people  have  been  led  to  explain  their  appearance 
under  such  circumstances  by  ''spontaneous  generation"; 
but  thus  far  the  facts  are  capable  of  other  explanation. 

229.  The  proper  spores  of  bacteria  (endospores)  are 
produced  singly  within  the  cells,  and  are  thick-walled, 
rounded  bodies.     By  the  breaking  of  the  filaments  into 


HIGHER  BLUE  GREENS  167 

their  component  cells  other  reproductive  bodies  (hormo- 
gones)  are  formed. 

230.  On  account  of  their  minuteness,  bacteria  may  be 
picked  up  by  currents  of  air  and  borne  long  distances, 
and  in  this  way  they  are  doubtless  often  carried  from 
place  to  place.  When  a  pool  of  putrid  water  dries  up, 
the  bacteria  with  which  it  swarmed  are  blown  away  with 
the  dust  and  dirt,  dropping  everywhere  into  pools,  upon 
plants  and  animals  living  and  dead,  and  even  entering 
our  lungs  with  the  air  we  breathe. 

Class  2.    HOLOPLASTIDEAE 
The  Higher  Blue  Greens 

231.  This  little  class,  of  about  20  species,  includes 
SHme  Algae,  in  which  the  nucleus  is  defined  by  a  nuclear 
membrane,  and  the  coloring  matter  is  concentrated  in 
one  or  more  plastids.  There  is  but  one  order,  the 
Glaucocystales,  and  a  single  family  (Glaucocystaceae)  of 
unicellular  plants.     The  type  genus  is  Glaucocystis. 

Laboratory  Studies  of  the  Myxophyceae.  With  the  fore- 
going sciicrul  statements  of  the  structure  and  life  of  the  Slime 
Algae  including  the  Bacteria,  the  student  must  now  make  some 
examination  of  them  by  means  of  a  good  compound  microscope 
in  the  laboratory.  In  his  examination  he  should  make  careful 
drawings  accompanied  by  brief,  necessary  descriptions.  It  is  a 
good  rule  in  the  study  of  plants  never  to  make  a  needless  draw- 
ing, nor  write  an  unnecessary  description.  A  second  rule  of  still 
greater  importance  insists  upon  the  absolute  truthfulness  (ac- 
curacy) of  both  drawings  and  descriptions. 

The  following  studies  are  suggested  as  useful. 

(a)  Scrape  off  a  little  of  the  greenish  slimy  matter  from  a 
damp  wall,  mounting  it  in  water;  examine  und.cr  a  liigli  power. 
Some  small  blue-green  or  smoky-green  cells  will  be  found 
belonging  to   the  Blue-green  Slimes   (Chroococcus,   etc.);  of 


168  PHYLUIM  I.     IVIYXOPHYCEAE 

these  some  will  probably  be  found  in  process  of  fission.  Larger 
br'ght-green  cells  filled  with  granular  protoplasm  will  also  be 
found;  these  are  species  of  Protococcus  belonging  to  the  next 
phylum. 

(h)  In  midsummer  look  along  the  water-line  of  fresh-water 
lakes  and  ponds  for  soft,  amber-colored,  round  masses  from  the 
s"ze  of  a  pea  to  that  of  a  hickory-nut.  By  mounting  a  small 
sl'ce  of  one  of  these  it  will  be  seen  under  the  microscope  to  be 
composed  of  mj^iads  of  filaments  of  Nostoc.  Occasionally  a 
filament  may  be  seen  with  a  heterocj^st;  its  function  is  not 
known. 

(c)  Secure  a  handful  of  the  dark-green  filamentous  growth 
which  is  common  on  the  wet  sides  of  watering-troughs  and 
place  it  in  a  dish  of  water.  If  an  Oscillatoria,  it  will  rapidly 
disperse  itself,  a  few  minutes  being  long  enough  to  show  quite 
a  change  in  position.  Now  mount  a  few  filaments  in  water  and 
examine  under  a  high  power.  They  will  be  seen  to  sway  from 
side  to  side  while  moving  quite  rapidly  across  the  field  of  the 
m'croscope. 

(d)  In  midsummer  scrape  off  one  of  the  small  jelly-like 
masses  of  Rivularia,  so  common  on  the  submerged  stems  of 
water-plants;  mount  in  water,  crushing  or  cutting  the  mass  so 
as  to  show  the  individual  filaments.  Each  filament  tapers 
from  the  center  of  the  mass  outw^ard,  and  at  its  larger  (inner) 
end  there  is  generally  a  heterocyst. 

Some  elementary  studies  of  bacteria  may  be  made  very  easily, 
but  their  profound  study  (Bacteriology)  involves  a  technique 
which  is  unattainable  by  the  beginner  in  Botany.  The  follow- 
ing may  be  attempted. 

(e)  Boil  a  pinch  of  cut  hay  or  any  other  similar  vegetable 
substance  for  a  few  moments,  and  put  into  a  glass  of  water; 
keep  in  a  warm  room  for  a  couple  of  days,  or  until  it  be- 
comes turbid  (from  the  abundance  of  bacteria);  examine  a 
minute  drop  with  the  highest  powers  of  the  microscope,  for 
active  bacteria.  The  bacterial  growth  originates  from  the 
si)ores  which  were  not  killed  by  the  short  boihng.  The  com- 
monest form  thus  obtained  is  Bacillus  subtilis. 

(/)  Put  a  bit  of  fresh  meat  into  water,  and  study  the  bacteria 
which  will  appear  in  it.  Spiral  forms  (especially  Spirillum) 
may  often  be  found  in  such  a  preparation. 

(g)  Examine  the  juices  of  decaying  fruits  and  vegetables. 


LABORATORY  STUDIES  169 

(It)  Amons  the  many  hacteriii  of  esi)ccial  iiitcroHt  to  us  are 
the  following: 

1.  Clover-nodule  bacteria  (Psendomonas  leguminosarum) , 
which  enrich  the  soil  by  the  i^'oduction  of  nitrogen  compounds. 

2.  Sulphur-bacteria  (Bcggiatoa  aiha),  which  occur  as  large 
motile  filaments  in  refrigerator  drains. 

3.  Apple  and  i)ear  blight  bacteria  {Bacillus  amylovorus), 
causing  the  blight  in  apple  and  pear  trees. 

4.  Cucumber-wilt  bacteria  {Bacillus  tracheiphilus) ,  causing 
the  ''wilt  disease"  of  cucumbers,  and  other  cucurbits. 

5.  Crown-gall  bacteria  {Pseudomonas  tumcfaciens) ,  causing 
the  crown  galls  in  the  roots  and  stems  of  many  plants. 

6.  Typhoid  fever  bacteria  {Bacillus  typhosus),  causing 
typhoid  fever. 

7.  Tuberculosis  bacteria  {Bacterium  tuberculosis),  causing 
tuberculosis. 

8.  Diphtheria  bacteria  {Bacterium  diphtheriae),  causing 
diphtheria. 

9.  Influenza  bacteria  {Bacterium  influenzae),  causing  influ- 
enza (''Grippe"). 

10.  Anthrax  bacteria  {Bacterium  anthracis),  causing  anthrax. 

11.  Cholera  bacteria  {Microspira  comma),  causing  cholera. 

12.  Colon  bacteria  {Bacillus  coli)  in  the  large  intestines  of 
most  mammals. 

LITERATURE  OF  MYXOPHYCEAE 

Here  as  elsewhere  only  the  most  necessary  works  are  men- 
tioned, in  the  order  of  their  desirability  for  the  beginner  in 
Botany. 

G.  S.  West,  A   Treatise    on    the    British    Freshwater    Algae, 

Cambridge,  1904. 
Josephine  E.  Tildex,  The  Myxophyccae  of  North  America  and 

Adjacent  Regions  (Vol.  I  of  Minnesota  Algae),  Minneapolis, 

1910. 
G.  B.  De  Toni,  Sylloge  Algarum,  Vol.  5,  Padua. 
E.  F.  Smith,  Bacteria  in  Relation  to  Plant  Diseases,  Washington, 

I,  1906;  II,  1911. 
W.   D.  Frost  and  E.  F.  Campbell,  A   Text-hook  of  General 

Bacteriology,  New  York,  1910. 


CHAPTER  VIII 
PHYLUM  II.  CHLOROPHYCEAE* 

THE   SIMPLE   ALGAE 

232.  The  plants  of  this  phylum  while  still  small,  and 
mostly  microscopic  and  consisting  of  single  cells,  fila- 
ments or  rarely  plates  of  cells,  show  a  considerable  ad- 
vance over  the  Slime  Algae  in  having  well-defined  nuclei, 
definite  plastids,  a  dominant  yellow-green  color  (chlor- 

ophyll  and  carotin),  and  in  many  genera 
sexual  reproduction.  The  cells  are  much 
better  developed,  the  walls  are  composed  of 
cellulose,  and  are  usually  firmer.  The  nu- 
FiG.  64— A    <^lear  matter  of  the  cell  is  collected  into  a 

rophyceae^^^°'  definite  uuclcus  which  is  surrounded  by  a 
membrane.     A  portion  of  the  protoplasm  is 

set  off  as  one  or  more  distinct  plastids  (chloroplasts) 

which  are  stained  green  by  chlorophyll. 

233.  Here  the  dominant  idea  is  the  definite  nucleus 
limited  by  a  nuclear  membrane.  With  this  are  associated 
the  definite  plastids,  true  chlorophyll,  firm  cell  wall, 
motile  reproductive  structures  (zoospores  and  gametes), 
and  the  still  simple  plant  body. 

234.  The  Simple  Algae,  of  which  there  are  about  1100 
species,  are  mainly  fresh-water  plants,  living  on  wet 
rocks,  moist  walls  or  tree-trunks,  etc.,  or  floating  or 
attached  in  the  deeper  waters.  A  few  have  become 
degenerated  through  parasitism. 

*  This  name  is  here  used  in  the  narrower  sense,  excluding  the 
plants  of  the  phyla  Zygophyceae  and  Siphonophyceae. 

170 


GREEN  SLIMES  171 

235.  This  phylum  has  been  unusually  productive  of 
other  phyla  of  primary  and  secondary  rank,  and  the 
suggestion  is  hazarded  that  also  from  it  (near  Proto- 
coccoideae)  a  phyletic  line  gave  rise  to  the  Animal  King- 
dom.    There  are  two  classes: 

I.  Plants  unicellular,  or  in  colonies. 

Class  3.  Protococcoideae 

II.  Plants  pluricellular,  in  filaments  (or  plates). 

Class  4.    CONFERVOIDEAE 

Class   3.     PROTOCOCCOIDEAE.     Green  Slimes 

236.  These  plants  (of  about  450  species)  are  nearly  all 
microscopic,  and  are  unicellular,  or  in  a  few  cases  aggre- 
gated into  definite  colonies.  They  propagate  (reproduce 
by  asexual  reproduction)  by  (1)  cell  division,  (2)  ciliated 
zoospores,  (3)  and  thick-walled  spores  (chlamydospores), 
and  generate  (reproduce  by  sexual  reproduction)  by  the 
union  of  equal,  motile  gametes  (isogametes)  to  form  a 
single  cell  (zygote)  which  often  becomes  a  thick-walled 
spore.     Generation  is  not  known  for  all  of  the  species. 

ORDER  PALMELLALES 

237.  These  unicellular  plants  are  not  aggregated  into 
colonies,  although  they  may  remain  attached  together 
in  irregular  masses  for  some  time  after  cell 

division.     They  are  common  in  water,  and    (o)    ^2>< 

in  moist  or  wet  places,  as  the  sides  of  walls, 

trees,   posts,   etc.,  where  they  often  form    (^^  fs^p) 

dense,  green  layers.     The  spherical  forms    ^^— ^  Ks^ 

growing  on  trees,  walls,  etc.,  which  produce      prol^eoccus 

no  zoospores  are  species  of  Protococcus, 

while    those    with    zoospores    may    be   Chlorococcum. 

Near  relatives  of  these  have  become  unicellular  para- 


172  PHYLUM  II.     CIILOROPHYCEAE 

sites  (Family  Synchytriaccae)  in  the  tissues  of  other  algae, 
or  even  land  plants,  and  are  known  as  Gall-fungi. 

ORDER  COENOBIALES 

238.  The  cells  or  coenocytes  in  these  plants  are  aggre- 
gated into  colonies,  the  most  common  of  which  are  the 

pretty  species  of  Scenedesmus,  in 
which  four  spindle-shaped  cells  lie 
side  by  side.  Less  common  is  the 
very  regular  plate-colony  of  Pedias- 
trum  with  usually  a  dozen  or  more 
regularly  arranged  coenocytes.  Re- 
T,     ^^    o       ,  lated   to    these    is    the    Water    Net 

riG.  GG. — Scenedosmus, 

dfcf'oi'"™  ''"'^  Hydro-  (Hydrodictyon)  with  its  many  long 
coenocytes  arranged  in  a  hollow, 
reticulated  colony  20  to  30  centimeters  long.  Ciliated 
zoospores  and  isogametes  occur  in  Pediastrum  and 
H3xlrodictyon. 

239.  Here  are  commonly  placed  certain  doubtful 
organisms,  the  Volvoces  (Volvox,  Pandorina,  and  related 
genera),  with  the  color  of  plants  but  the  structure  of 
animals.  Most  botanists  still  claim  them  on  account  of 
their  color,  but  many  zoologists  emphasizing  the  impor- 
tance of  their  structure  regard  them  as  animals  (Flag- 
ellata).  The  explanation  here  given  is  that  at  about 
this  point  in  the  Vegetable  Kingdom  the  animal  type  be- 
came differentiated  from  the  plant  type  by  an  increase 
in  the  motility  of  the  cells,  and  in  the  Volvoces  we  have 
the  organisms  on  the  pathway  leading  from  plants  to 
animals.  In  the  opinion  of  the  authors  they  have  already 
passed  the  frontier  of  the  Plant  Kingdom,  and  entered 
that  of  Animals,  although  they  have  not  yet  abandoned 
their  use  of  chlorophyll. 

240.  On  the  same  ground  should  be  excluded  the  ''red 


CONFERVAS 


173 


snow  plant''  of  high  mountains  and  polar  regions,  a 
unicellular  ciliated  organism  (Chlamydomonas)  which  is 
usually  of  a  red  color,  and  some  more  common  but  similar, 
often  red,  organisms  (Haematococcus)  found  in  pools  and 
on  wet  earth.  They  are  all  more  like  animals  than 
plants. 

Class  4.     CONFERVOIDEAE.     Confervas 


241.  The  Confervas  are  simple  or  branched  filaments  of 
cells,  or  a  sheet  (plate)  of  cells,  and  number  about  G40 
species.  They  propagate  by  (1)  the  fracture  of  the 
filaments  (into  hormogones),  (2)  ciliated  zoospores,  (3) 
thick- walled  spores  (chlamydospores),  and  generate  by 
the  union  of  isogametes  or  heterogametes,  to  form  a 
zygote  which  often  becomes  a  thick-walled  spore.  They 
are    mostly    fresh-water    plants,    in 

ponds  and  in  running  waters.  W^(    ^ 

242.  The  simplest  of  the  Confervas  jf(  ' 
are  small  unbranched  filaments  (spe- 
cies of  Ulothrix)  which  are  usually 
attached  by  a  basal  cell  (''root"). 
They  propagate  by  2-  or  4-ciliated 
zoospores,  and  generate  by  the  union 
of  2-ciliate  gametes. 

243.  The  very  similar,  much-branched  and  rooted 
Draparnaldia  and  Chaetophora  present  a  slightly  higher 
development  of  the  same  type.  They  are  common  in 
running  fresh  water. 

244.  Kelated  to  these  are  the  Sea-Lettuces  common  on 
stones,  wharf-timbers,  etc.,  along  the  coast  and  in  brack- 
ish waters,  and  resembling  small  lettuce  leaves.  Each 
plant  consists  of  a  single  layer  of  cells  (JNIonostroma)  or 
two  layers  (Ulva),  and  nearly  every  cell  is  capable  of 


Fig.  67.— Ulothrix  and 
Monostroma. 


174 


PHYLUM  II.     CHLOROPHYCEAE 


Fig.  68. 
Oedogonium. 


producing  4-ciliate  zoospores,  or  2-ciliate  gametes.  The 
irregularly  tubular  Enteromorphas  resemble  the  Sea 
Lettuces  and  are  oommon  in  brackish  ponds. 

245.  In  the  Oedogoniums  {Ocdogoniaceae)  the  plants 
are  attached  below,  and  are  simple  or  branched  above. 
They  propagate  by  means  of  multiciliated  zoospores  which 
are  formed  singly  in  the  cells,  and  generate  by  hetero- 
gametes,  consisting  of  small  multiciliated  sperms,  and 

large  non-ciliated  eggs.  The  sperms  are 
formed  (1)  in  certain  cells  in  the  filament 
which  produces  the  eggs,  or  (2)  in  some- 
what smaller  filaments,  or  (3)  in  very 
small,  few-celled  filaments  ("dwarf  males"). 
The  eggs  are  formed  singly  in  oogones  that 
are  merely  transformed  and  considerably 
enlarged  vegetative  cells.  When  the  egg 
reaches  maturity  the  oogone  wall  opens  to  admit  the 
sperm,  after  which  the  egg  becomes  a  thick-walled  rest- 
ing spore.  In  germination  the  resting  spore  divides  into 
four  multiciliated  zoospores  which  soon  come  to  rest  and 
develop  into  ordinary  vegetative  filaments. 

246.  The  little  Disk  Algae  (Coleochaetaceae)  are  minute 
branching  plants  closely  related  to  the  Oedogoniums, 
whose  radiating  filaments  usually  fuse  later- 
ally into  small  disks  or  cushions,  a  milli- 
meter or  so  in  diameter,  and  occurring  on 
the  stems  and  leaves  of  larger  water  plants. 
They  propagate  by  biciliated  zoospores 
formed  singly  in  the  cells,  and  generate  by 
heterogametes.  The  biciliated  sperms  are 
formed  singly  in  the  antheridial  cells. 
The  oogones  are  terminal  and  each  contains 

a  single  egg,  and  is  supplied  with  a  tubular  prolongation, 
the  'Hrichogyne.'^ 


Coleochaete. 


DISK  ALGAE  175 

247.  Fertilization  is  effected  by  a  sperm  uniting  with 
the  egg  in  the  oogone,  usually  by  passing  into  the  open 
end  of  the  trichogyne.  After  fertilization  the  egg  in- 
creases considerably  in  size,  and  forms  a  cellulose  coat  of 
its  own.  The  cells  which  support  the  oogone  send  out 
lateral  branches,  which  grow  up  and  closely  surround  it, 
finally  covering  it  entirely  (excepting  the  trichogyne) 
with  a  cellular  thick- walled  '^pericarp. ''  The  whole  mass, 
including  the  fertilized  oogone  and  its  investing  pericarp, 
constitutes  the  simplest  form  of  spore-fruit  (sporocarp). 

248.  The  further  growth  of  the  spore-fruit  takes  place 
the  next  spring  by  the  swelling  of  the  protoplasmic  con- 
tents, and  the  consequent  rupture  of  the  pericarp;  the 
inner  portion  divides  into  several  cells  (the  proper  fruit- 
spores),  which  give  rise  to  zoospores  closely  resembling 
those  developed  from  the  vegetative  cells.  From  each 
zoospore  a  new  plant  eventually  arises. 

There  is  but  one  genus  (Coleochaete)  including  a  few 
widely  distributed  species. 

Laboratory  Studies,  (a)  Scrape  off  a  little  of  the  green, 
paint-like  coating  from  a  flower-pot,  a  damp  wall,  or  a  side- 
walk plank,  and  examine  under  a  high  power  for  common 
Green  Slime  (Protococcus,  etc.). 

(6)  Gall-fungi  may  sometimes  be  found  in  Spirogyra  and 
Desmids,  and  in  the  leaves  of  evening  primroses,  plantains, 
mints,  and  some  leguminous  plants. 

(c)  Examine  the  green  })lants  collected  from  ponds  and 
ditches  for  Sccnedesmus  and  Pediastrum.  The  former  may 
often  be  found  in  great  numbers  on  the  glass  sides  of  jars  or 
aquaria. 

{d)  In  midsummer  search  quiet  pools  for  Water  Nets.  With 
a  fine  scissors  cut  out  a  piece  of  one  and  mount  carefully  in 
water.  Stud}^  with  a  low  power  of  the  microscope.  Some  of 
the  coenocytes  will  })e  found  producing  zoospores.  Search 
for  young  nets  forming  within  the  old  coenocytes. 

(e)  Collect  fresh  specimens  of  Sea  Lettuce,  put  into  a  jar  of 


176  PHYLUM  II.     CHLOROPHYCEAE 

water,  and  watch  the  jiroduetion  of  zoospore^.  Knteromorpha, 
which  is  common  in  brackish  waters  in  the  interior,  may  be 
substituted  for  Ulva. 

(/)  Study  Ulothrix  in  hke  manner.  It  may  be  grown  in  an 
aciuarium  very  easily,  so  as  to  be  obtainal^le  at  an}^  time,  even 
in  the  winter.  Draparnaldia  ma}'  be  found  in  running  fresh 
water. 

(g)  Specimens  of  Oedogonium  may  l)e  obtained  by  examining 
the  small  sticks  and  stems  of  aquatic  plants  from  quiet  waters. 
They  may  be  recognized  by  the  enlarged  oogones. 

(h)  The  Disk  Algae  occur  in  fresh-water  pools  as  little  green 
masses  adhering  to  leaves,  sticks,  the  stems  of  living  plants, 
etc.,  where  they  should  be  sought.  The  sexual  process  and 
the  development  of  the  sexual  organs  occur  in  May,  June,  and 
July. 

LITERATURE  OF  CHLOROPHYCEAE 

Frank  S.  Collins,  The  Green  Algae  of  North  America,  Tufts 
College,  1909. 

G.  S.  West,  A  Treatise  on  the  British  Fresh-water  Algae,  Cam- 
bridge, 1904. 


J 


CHAPTER  IX 

PHYLUM  III.     ZYGOPHYCEAE 

THE  CONJUGATE  ALGAE 

249.  These  plants  are  typically  unbranched,  unat- 
tached filaments,  which  easily  fragment  into  short 
segments,  or  single  cells.  They  are  green,  with  chloro- 
phyll, but  in  many  cases  this  is  obscured  by  the  presence 
of  a  yellow-brown  pigment  in  the  cells.  They  propagate 
by  the  fission  and  ultimate  separation  of  cells  (hormo- 
gones)  or  by  the  formation  of  spores,  but  are  wholly 
destitute  of  zoospores.  They  generate  by  the  union  of 
the  protoplasm  of  pairs  of  ordinary  cells  (isogametes). 

250.  The  dominant  idea  in  this  phylum  is  the  physio- 
logical sluggishness  of  the  cells,  resulting  in  the  feeble 
attachment  of  the  cells  to  one  another  and  the  easy  and 
usually  early  fragmentation  of  the  filament,  the  absence 
of  zoospores,  and  the  reduction  of  the  sexual  roi)roduction 
to  the  sluggish  union  of  the  scarcely  modified  proto- 
plasms of  two  vegetative  cells.  This  is  a  phylum  on  the 
down-grade,  and  all  of  its  members  show  more  or  less 
structural   degeneration. 

There  are  two  classes: 

I.   Chloroi)hyll  p;rceii  phiiits  with  cellulose  walls. 

Class  5.    CONJUGATAE. 

II.  Mostly   yellowish-brown   plants,    with   silicificd   walls. 

Class  G.  Bacillarioideak. 
12  177 


178  PHYLUM  III.     ZYGOPHYCEAE 

Class  5.  CONJUGATAE 
In  this  class  the  lowest  type  is  that  of  the  filamentous 
Pond  Scums,  well  represented  everywhere  by  species  of 
Spirogyra.  In  this  genus  the  ribbon-shaped  chloro- 
plasts  are  longer  than  the  cells,  and  are  therefore  more  or 
less  spirall}^  coiled.  In  generation  two  cells  unite  by 
pushing  out  short  opposing  tubes  until  they  come  in 

contact;  the  contact  walls  then  are 

absorbed  leaving  an  open  channel 
from  cell  to  cell,  and  through  this 
the  protoplasm  from  one  cell  slowly 
fH.  70.— Spirogyra.  passcs  to  the  othcr,  the  two  proto- 
plasms uniting  into  one  mass,  which 
rounds  up  and  covers  itself  with  a  thick  wall,  thus 
forming  a  resting  spore.  The  resting  spore  thus  formed 
is  set  free  by  the  decay  of  the  dead  cell- walls  of  the  old 
filament  surrounding  it;  it  then  falls  to  the  bottom  of  the 
water,  and  remains  there  until  the  proper  conditions  for 
its  growth  appear. 

251.  More  commonly  this  sexual  union  takes  place 
between  cells  of  different  filaments,  as  described,  but  in 
some  species  such  a  union  takes  place  between  contigu- 
ous cells  in  the  same  filament,  the  tubes  forming  at  the 
contiguous  ends. 

252.  The  germination  of  the  resting  spore  is  a  simple 
process.  The  inner  mass  enlarges  and  bursts  the  outer 
hard  coat;  it  then  extends  as  a  cylindrical  cell,  in  which 
after  a  while  a  transverse  partition  forms,  and  this  is 
followed  by  another  and  another,  until  an  extended 
filament  is  produced. 

253.  In  the  Desmids  the  filaments  usually  fragment 
easily  into  single  cells,  which  then  grow  more  or  less  after 
separation.  However  in  the  lower  Desmids  the  cells  are 
still  in  filaments  (Family  Desmidiaceae).     In  the  second 


I 


DESMIDS  179 

family  {Closteriaceae)  the  elongated  cylindrical  cells  sepa- 
rate early  and  become  more  or  less  attenuated,  as  in 
Closterium.  In  a  third  family  (Cosma- 
riaceae)  the  flattened,  more  or  less  con- 
stricted cells  separate  very  early,  and 
in  many  cases  become  terminally  much 
lobed  or  otherwise  modified.  Of  the 
less    modified    desmids    the    species    of     Fig.ti.— Desmids: 

j^  .  ,  1  1  •!        Closterium,     Cosma- 

Cosmarmm    are   good   examples,    while  num.    and    Micra- 
those  of  Euastrum  and  Micrasterias  are 
greatly  modified,  the   cells  of  the  latter  being  divided 
into  mam'  pointed  lobes. 

254.  In  generation  the  desmid  cells  break  open  at  the 
middle  (where  there  is  commonly  a  joint  in  the  wall)  and 
the  two  protoplasms  (isogametes)  unite  into  a  zygote, 
which  eventually  becomes  a  thick-walled  resting  spore. 
After  some  time  the  resting  spore  germinates  by  ruptur- 
ing its  wall  and  dividing  the  contents  into  two,  four  or 
eight  new  non-ciliated  cells  which  eventually  become  like 
the  parent  cells. 

255.  Desmids  are  fresh-water  plants,  floating  free  in 
the  waters  of  quiet  pools,  or  entangled  with  mosses  or 
other  aquatic  plants. 

Class  G.  BACILLARIOIDEAE 

256.  The  plants  of  this  class  are  the  Diatoms,  num- 
bering about  5700  species,  or  even  as  many  as  10,000 
species  in  the  opinion  of  some  botanists.  Some  diatoms 
are  filamentous,  but  in  the  greater  number  the  filaments 
fragment  early  into  single  cells.  The  cells  contain 
chlorophyll,  which  is  commonly  hidden  by  the  addition 
of  diatomin,  a  yellow-brown  pigment.  A  few  diatoms 
are  colorless,  and  hysterophytic,  and  therefore  are 
''fungi.'' 


180  PHYLU:\r  III.     ZYGOPHYCEAE 

257.  Tlic  ccUulusc  walls  in  most  tliatoms  soon  1)C('ome 
more  or  less  silicified  and  rigid,  and  incapable  of  further 
expansion.  This  is  proV)ably  a  protective  device,  many 
diatoms  Hving  at  or  near  the  surface  of  the  ocean  waters 
where  softer  walls  would  be  likely  to  be  crushed.  This 
rigidity  of  their  walls  has  brought  about  some  structural 
details  that  are  peculiar  to  this  group  of  plants,  and 
which  are  quite  puzzling  to  the  beginner  if  not  considered 
in  connection  with  the  origin  of  diatoms  and  their  rela- 
tionship to  the  filamentous  types. 

258.  In  order  to  understand  the  structure  of  any 
diatom  it  is  necessary  to  consider  it  as  one  cell  of  a 
cylindrical,  angled,  or  flattened  filament.  These  cells 
are  usually  short  (measured  along  the  axis  of  the  fila- 
ment), so  that  when  separated  from  the  other  cells  they 
lie  with  one  end  up,  and  thus  show  a  cross-section  of  the 
filament.  Compare  this  with  the  end  view  of  the  cells 
in  a  filamentous  plant  like  Ulothrix  or  Spirogyra.  As  in 
Desmids,  the  cells  of  the  Diatoms  are  transversely 
jointed,  allowing  the  two  halves  (really  the  two  ends  of 
the  cells)  to  move  apart,  and  thus  enlarge  the  cell  cavity. 
Each  half  of  the  silicified  wall  is  shaped  like  a  paper  box 
cover,  the  flat  surface  corresponding  to  the  ''valve"  and 
the  curving  ring  to  the  ''girdle."     Sometimes  there  are 

additional  rings  known  as  "  interzones, "  giv- 
ing a  good  deal  of  flexibility  to  the  diatom 
cell  wall. 

259.  Diatoms  propagate  (1)  by  the  enlarge- 
ment of  the  protoplasm  of  the  cell  resulting  in 
its  elongation,  and  the  formation  of  two  walls 
propagiui^  in  the  plane  of  the  joint  which  become  the 
of  a  diatom.    ^^^^  ^f  ^j^^  ^^^.^  ^^^^  ^^^g  (''fission");  (2)  by 

the  separation  of  the  two  halves  of  the  cell  allowing  the 
escape  of  the  protoplasm  which  then  rapidly  grows  into  a 


DIATOMS  LSI 

larger  now  coll  (''rojuvonosccnce").  Thoy  gonorato  ])y 
tlio  oscapo  and  union  of  tlio  protoplasms  of  two  contigu- 
ous colls  whose  half-cells  have  separated,  resulting  in  the 
formation  of  one  or  two  new  and  usuall}-  much  larger 
cells.  Small  biciliate  isogametes  have  been  doubtfully 
reported  in  some  marine  diatoms. 

260.  There  are  two  general  kinds  (orders)  of  Diatoms, 
namely,  the  Round  Diatoms  (Eupodiscales)  with  the  cells 
mostly  round  in  end  view,  and  the  Flat  Diatoms 
{Xaviculales)  with  the  filaments  flattened  in  end  view. 

261.  The   Round    Diatoms    are   mostly 

marine  and  fossil.  The  ends  of  the  cells  J  .  1 ,  1  .L.L 
are  usually  marked  radially  with  lines  or  (^ 

rows  of  dots,  as  in  Melosira,  Coscinodiscus,  fig.  73.— a 
Actinodiscus,  etc.  Some  Round  Diatoms  Meioglr?!^"'"'"' 
form  long  filaments  (Melosira). 

262.  The  Flat  Diatoms  occur  abundantly  as  fresh- 
water, marine,  and  fossil  plants.     The  ends  of  the  cells 

(transection  of  the  flat  filament)  are  often 
marked  transversely  or  pinnately  by  dots  or 
lines.  In  many  of  our  most  common  Flat 
Diatoms  (e.g.  Naviculaccae)  there  is  a  me- 
dian longitudinal  slit  (''raphe")  in  the  end 
FiS^D^at^n^  wall,  which  probabl}^  has  to  do  with  the  mo- 
Baciiiaria.      '    ^-j-^^.  cxhi))ited  by  thoso  pUiuts  (Par.  174). 

263.  Origin  of  Zygophyceae.  It  may  be  assumed  that 
the  plants  of  this  phylum  have  been  derived  from  other 
filamentous  plants,  and  that  the  adhesion  of  cell  to  coll, 
and  the  consequent  formation  of  a  multicellular  plant 
body,  had  l)ocome  a  well  established  habit  long  before 
the  peculiarties  arose  which  set  them  off  as  Zygophy- 
ceae. We  must  search  among  the  Confervoideae  of  the 
pnH'oding  phylum  for  the  ancestral  tyi)os  from  whioh  the 
Conjugate  Algae  may  have  descended.     Such  plants  as 


182  PHYLUM  III.     ZYGOPHYCEAE 

IMicrospora  and  Ulothrix  could  very  well  serve  as  the 
originals  which  have  been  modified  successively  into 
the  Pond  Scums,  the  Desmids  and  the  Diatoms.  The 
limited  fragmentation  of  the  filament  in  Ulothrix  is  so 
much  increased  in  the  Conjugate  Algae  as  to  render  the 
production  of  zoospores  unnecessary.  In  like  manner 
the  sluggish  protoplasm  of  the  Conjugate  Algae  is  corre- 
lated with  the  disappearance  of  the  freely  motile  gametes 
and  the  degeneration  of  the  sexual  process  into  a  sluggish 
conjugation,  which  in  some  Desmids  and  Diatoms  results 
in  the  partial  (if  not  complete)  suppression  of  the  sexual 
act.  According  to  this  view  ''conjugation"  is  the  result 
of  degeneration.  It  is  sexual  reproduction  on  its  way 
toward  disappearance.  Instead  of  affording  an  example 
of  the  beginning  of  sexuality,  as  has  so  often  been  sug- 
gested, these  plants  show  sexuality  on  its  way  to  disap- 
pearance. Furthermore,  it  is  obvious  that  the  Conjugate 
Algae  constitute  a  lateral  phylum  which  is  related  to 
other  phyla  only  in  its  lower  members,  and  that  its  higher 
members  depart  more  and  more  widely  from  all  other 
forms  of  plants. 

Laboratory  Studies,  (a)  Collect  a  quantity  of  bright  green 
pond  scum,  which  always  abounds  in  shallow  ponds  and  pools  in 
the  spring,  summer  and  autumn,  and  preserve  in  a  dish  of 
water.  Collect,  also,  some  which  has  begun  to  turn  yellow  and 
brown.  Upon  mounting  a  little  of  the  first  in  water  and  exam- 
ining with  a  high  power  it  will  be  found  to  consist  of  threads 
of  cylindrical  cells,  each  containing  one  or  more  spiral  chloro- 
plasts  (Spirog>Ta)  or  star-shaped  chloroplasts  (Zygnema). 
Upon  mounting  some  of  the  second  collection,  here  and  there 
the  formation  of  resting  spores  may  be  observed.  In  all  cases 
care  must  be  taken  not  to  mount  too  great  a  quantity  of  the 
material,  nor  to  injure  the  plants  }:)y  rough  handling. 

(b)  Collect  a  quantity  of  pond  scum  and  other  aquatic 
vegetation.  IMount  portions  of  this  material  and  search  for 
desmids,  using  a   low  power  objective.     Two-lobed  desmids 


LABORATORY  STUDIES  183 

(Cosmarium)  of  a  bright  green  color  may  frequently  be  found. 
The  hirge  kuiatc  desmids  (Closteriuni)  are  often  more  common. 
In  the  hitter  the  clear  protoplasm  at  each  end  is  always  stream- 
ing rai)idly. 

(c)  Round  Diatoms  may  be  obtained  of  dealers  in  laboratory 
material,  or  mounted  slides  may  be  used.  A  few  Round 
Diatoms  may  be  found  occasionally  in  fresh-water  ponds,  and 
they  often  occur  on  the  surfaces  of  marine  seaweeds. 

(d)  Collect  a  little  of  the  brownish-yellow  scum  which  in 
earl}^  si)ring  gathers  on  the  top  of  the  water  of  brooks,  ditches, 
and  pools.  Mount  in  water  and  examine  with  a  high  power. 
Hundreds  of  Flat  Diatoms  may  be  seen  moving  rapidl}-  in 
ever}^  direction  across  the  field.  In  any  such  preparation  many 
species  of  various  shapes  will  be  found.  The  prevailing  forms, 
however,  are  much  flattened  and  somewhat  diamond  shaped 
in  end  view. 

(e)  Study  in  like  manner  the  slimy  coating  upon  dead  leaves 
and  twugs  in  water  in  the  summer  for  diatoms.  On  some  of 
these  very  fine  markings  ma}^  be  found. 

(/)  Here  again  mounted  shdes  of  Flat  Diatoms  may  be 
used  with  profit,  but  it  is  well  to  study  Kving  specimens  so  as 
to  be  able  to  observe  their  motihty. 

(g)  For  future  study  in  the  laboratory  the  Conjugate  Algae 
should  be  preserved  in  bottles  of  water  containing  just  enough 
alcohol,  glycerine,  formaldehyde  or  carbolic  acid  to  prevent 
their  decay.  One-fourth  or  fifth  of  the  first  and  second,  one- 
tenth  of  the  third,  and  enough  of  the  last  to  give  a  decided 
odor,  will  usually  do  well  enough.  A  2  per  cent,  solution  of 
potassium  acetate  made  light  blue  by  addition  of  copper  suljihate 
will  preserve  the  green  color  of  these  i)lants,  if  kept  in  the  dark. 

LITERATURE  OF  ZYGOPHYCEAE 

0.  S.  West,  A  Treatise  on  the  British  Fresh-water  Algae,  Cam- 
bridge, 1904. 

Frank  S.  Collins,  The  Green  Algae  of  North  America,  Tufts 
College,  1909. 

0.  B.  De  Toni,  Sylloge  Algarum,  Vol.  II,  Padua  1S91-1S94. 

H.  Van  Heurck.  ^l  Treatise  on  the  Diatomaccac  (Engl,  trans.), 
London,  1896. 


chapti:r  X 

PHYLUM  IV.     SIPHONOPHYCEAE 

THE  TUBE  ALGAE 

264.  These  plants  are  filamentous,  saccate  or  erect- 
dendroid,  and  are  composed  of  coenocytes  instead  of  dis- 
tinct cells.  In  the  first  (primitive)  forms  the  plant  body 
consists  of  a  row  of  long  bi-  or  poly-nucleated  segments 
(coenocytes)  arranged  in  a  simple  or  branched  filament, 
which  is  more  commonly  rooted  below.  When  the  fila- 
ment has  cross  partitions  it  is  said  to  be  septated.  In 
many  Tube  Algae  there  are  no  partitions  in  the  vegeta- 
tive portions  of  the  plant,  and  such  are  said  to  be 
continuous. 

265.  They  are  propagated  (1)  by  the  internal  division 
of  the  protoplasm  of  a  coenocyte  (sporangium),  or  even  of 
the  whole  plant  into  spores  (ciliated  zoospores  in  the 
water — walled  spores  in  the  air) ;  (2)  by  the  condensation 
of  definite  masses  of  protoplasm  directly  into  thick-walled 
spores  (chlamydospores).  Their  generation  shows  all 
gradations  including  the  union  of  (1)  ciliated  isogametes; 
(2)  ciliated  heterogametes;  (3)  ciliated  sperms,  with  eggs; 
(4)  antherid  nuclei,  with  eggs — in  all  cases  producing 
zygotes,  which  usually  become  thick-walled  resting 
spores. 

266.  The  dominant  idea  here  is  the  development  of 
coenocytes  instead  of  distinct  cells,  and  this  has  been 
consistently  adhered  to  even  when  the  plant  body  has 
shown  otherwise  a  considera])le  amount  of  differentiation. 

184 


CLADOPHORA  AXD  VAUCHERIA 


1S5 


267.  They  are  typically  aquatic,  green  plants  (holo- 
phytes),  but  many  have  become  parasites  or  saprophytes, 
and  suffered  degradation  into  ''fungi"  (hysterophytes). 
The  number  of  species  now  known  is  about  1260.  The 
holophytes  are  readily  separated  into  two  classes,  the 
Lower  Tube  Algae  (Vaucherioideae)  and  the  Higher 
Tube  Algae  (Bryopsidoideae),  and  from  the  first  have 
been  derived  a  considerable  number  of  hysterophytes 
which  may  be  separated  as  a  class  of  Tube  Fungi,  or 
Lower  Fungi  (Phycomyceteae). 

268.  Water  Flannel  (Cladophora)  is  one  of  the  com- 
monest genera  of  the  Lower  Tube  Algae,  occurring  in 
large  tangled  masses  of  stout  branched  fila- 
ments in  fresh-water  streams,  or  even  in 
salt  waters.  Its  coenocytes  have  thick 
w^alls,  with  two  to  many  nuclei.  In  their 
propagation  and  generation  they  so  closely 
resemble  Ulothrix  and  Microspora  that  they 
were  formerly  included  in  the  same  famil3^ 
Zoospores   with   two   or   four   ciUa    escape 

from  the  segments  and  after  a  free-swimming  period 
come  to  rest  and  grow  directly  into  new  plants.  Like- 
wise biciliated  isogametes  issue  from  similar  segments, 
and  fuse  into  zygotes. 

269.  The  Green  Felts  (Vaucheria)  are  good  repre- 
sentatives of  one  of  the  families  in  which  the  plant  body 

is  a  continuous  coenocyte.  They  are 
coarse,  green,  tubular,  branching  and 
rooted  plants  which  grow  in  abun- 
dance on  the  moist  earth  in  the  vicinity 
of  springs,  and  in  shallow  running 
water,  forming  dense  felted  masses. 

270.  They  propagate  by  large  compound  motile  zoo- 
spores, formed  in  the  ends  of  the  branches.     Each  zoo- 


FiG.  75. 
Cladophora. 


Fig.  76. — Vaucheri; 


186  PHlTU^r  IV.     SIPHONOPHYCEAE 

spore  eventually  forms  a  wall  around  itself,  and  then 
proceeds  to  elongate  into  a  new  plant-body. 

271.  Generation  takes  place  in  special,  usually  lateral, 
segments.  Both  antherids  and  oogones  develop  as  pro- 
tuberances upon  the  stem.  The  antherid  is  long  and 
rather  narrow,  and  soon  much  curved;  its  upper  portion 
becomes  cut  off  by  a  partition,  and  in  it  very  small  bi- 
ciliated  sperms  are  developed  in  great  numbers.  The 
oogone  is  short  and  ovoid  in  outline,  and  usually  stands 
near  the  antherids.  In  it  a  partition  forms  at  its  base; 
the  upper  portion  becomes  an  oogone,  and  its  protoplasm 
condenses  into  a  rounded  body,  the  egg.  At  this  time 
the  wall  of  the  oogone  opens,  and  permits  the  entrance  of 
the  sperms  which  were  set  free  by  the  rupture  of  the 
antherid  wall. 

272.  Upon  coming  into  contact  with  the  egg  one  sperm 
fuses  with  it;  the  fertilized  egg  (zj^gote)  immediately 
begins  to  secrete  a  wall  of  cellulose  about  itself,  and  it 
thus  becomes  a  resting  spore.  After  a  period  of  rest  the 
thick  wall  of  the  resting  spore  splits,  and  through  the 
opening  a  tube  grows  out  which  eventually  assumes  the 
form  and  dimensions  of  the  full-grown  plant. 

Here  must  be  placed  half  a  dozen  families  of  hystero- 

phytic  plants,  the  ''Tube  Fungi,"  often  known  as  the 

''lower  fungi,"  and  to  be  regarded  as  degen- 

j{i  erate  descendants  of  some  such  holophytic 

'  form  as  Vaucheria. 

273.  The  Water-molds   {Saprolegniaceae) 
are  colorless  saprophytes  or  parasites.     They 
are   generally   to   be   found    in   the   water, 
Saproiegnia.     attached   to   the   bodies  of   living  or  dead 
fishes,  crayfishes,  etc.,  or  in  decaying  animal 
or  vegetable  matter,  in  or  out  of  the  water.     The  plant- 
body  is  greatly  elongated  and  much  branched,  and  is 


WATER  MOLDS  187 

basally  rooted.  All  its  vegetative  portion  is  continuous; 
the  reproductive  portions  only  are  separated  from  the 
rest  of  the  plant-body  by  partitions. 

274.  The  propagation  is  very  much  the  same  as  in 
Green  Felt.  It  may  be  briefly  described  as  follows  for 
Saprolegnia:  The  protoplasm  in  the  end  of  a  branch 
becomes  somewhat  condensed,  a  partition  forms,  cutting 
off  this  portion  from  the  remainder  of  the  filament,  and 
the  whole  of  its  contents  becomes  converted  by  inter- 
nal cell  division  into  zoospores  provided  with  two  cilia. 
These  soon  escape  from  a  fissure  in  the  wall  and  are  active 
for  a  few  minutes,  after  which  they  come  to  rest  and  their 
cilia  disappear.  In  one  or  two  hours  they  germinate  by 
sending  out  a  filament,  from  which  a  new  plant  is  quickly 
produced. 

275.  The  sexual  organs  also  bear  a  close  resemblance 
to  those  of  Green  Felt.  The  oogones  are  spherical,  or 
nearly  so  (in  most  of  the  species),  and  contain  from  one 
to  many  eggs,  which  are  fertilized  by  means  of  antherids, 
which  usually  develop  as  lateral  branches  just  below  the 
oogones.  Fertilization  takes  place  by  the  direct  contact 
of  the  antherid  and  the  passage  of  its  contents  into  the 
oogone  by  means  of  a  tubular  process  from  the  former. 
In  some  species  there  is  no  transfer  of  the  contents  of 
the  antherid,  and  in  others  again  there  are  no  antherids. 
These  eggs  must  therefore  develop  without  fertilization, 
indicating  that  sexuality  is  disappearing  in  these  plants. 
Eventually  each  egg  becomes  covered  with  a  wall  of 
cellulose  and  is  thus  transformed  into  a  resting  spore, 
which  later  germinates  by  sending  out  a  tube,  as  in 
Green  Felt. 

276.  The  Downy  Mildews  {Peronosporaceae)  and 
White  Rusts  (Alhuginaccae)  live  parasitically  in  the 
tissues  of  higher  plants.     They  are  composed  of  long 


188  PHYLUM  IV.     SIPHONOPHYCEAE 

brant'liino;  tubes,  whose  cavities  are  continuous  through- 
out. They  usually  grow  between  the  cells  of  their  hosts, 
and  draw  nourishment  from  them  ])y  means  of  little 
Dranches  Hiaustoria),  which  thrust  them- 
selves through  the  walls. 

277.  The  asexual  spores  (conidia)  are 
produced  upon  branches  (conidiophores) 
which  protude  through  the  epidermis  of 
Fig.  78.— Piasmopara  the  host.  In  the  Downy  Mildews  (Per- 
onospora,  Phytophthora,  Piasmopara, 
etc.  ) these  branches  find  their  way  through  the  breath- 
ing-pores and  bear  their  spores  singly  upon  lateral  branch- 
lets;  in  the  White  Rusts  (Albugo)  the  conidia-bearing 
branches  collect  under  the  epidermis  and  rup- 
ture it.  Here  the  conidia  are  borne  in  chains 
or  bead-like  rows. 

278.  In  some  genera  the  relationship  to  the 
Water  Molds  is  shown  by  the  fact  that  these 
conidia  upon  falling  into  water  become  true 
sporangia,  within  which  few  to  many  zoospores 
are  produced.  These  after  a  free-swimming  period  be- 
come motionless  and  germinate  by  means  of  a  tube  which 
bores  its  way  into  the  host.  In  two  genera,  however 
(Bremia  and  Peronospora),  the  conidia  themselves  germ- 
inate directly  by  a  tube. 

279.  The  sexual  reproduction  takes  place  in  the  inter- 
cellular spaces  of  the  host.  Lateral  branches  of  two  kinds 
appear  upon  the  hyphae;  those  of  one  kind  (the  young 
oogones)  become  greatly  thickened  and  finally  assume  a 
globular  shape;  the  other  branches  (the  young  antherids) 
become  elongated  and  club-shaped,  both  becoming  sepa- 
rated from  the  main  filament  by  cross  partitions.  The 
antherid  comes  in  contact  with  the  oogone  which  it 
penetrates  by  a  tube,  through  which  fertilization  occurs, 


BLACK  MOLDS  LS9 

and  th('reu])oii  the  egg  socretes  a  thick  doubh'  wall,  and 
becomes  a  resting  spore. 

280.  The  resting  spores  remain  in  the  tissues  of  the 
host  until  the  latter  decay,  which  is  generally  in  the 
spring.  Germination  then  takes  place,  in  some  species 
by  the  production  of  a  tube  (either  germ-tul)e,  or  co- 
nidiophore),  in  others  by  the  division  of  the  protoplasm 
into  zoospores  whose  subsequent  development  is  like 
that  described  above  in  case  of  the  conidia. 

281.  The  Black  Molds  (Miicoraceac)  are  saprophytic 
and  sometimes  parasitic  plants;  they  are  composed  of 
long  branching  non-septate  filaments  (hj^phae),  which 
ahvays  form  a  more  or  less  felted  mass,  the  mycelium. 
The  protoplasmic  contents  of  the  filaments  are  more  or 
less  granular,  but  they  never  develop  chlorophyll.  The 
cell  walls  are  colorless,  except  in  the  fruiting  filaments, 
which  are  often  dark-colored  or  smoky  (fuliginous); 
hence  the  name  of  Black  Molds. 

282.  The  mycelium  sometimes  develops  exclusively  in 
the  interior  of  the  nutrient  medium;  in 
other  cases  it  develops  partly  in  the  me- 
dium and  partly  in  the  air.  In  some 
species  the  mycelium  may  attack  the  fila- 
ments of  other  plants  of  the  same  order, 
and  even  exhibit  a  weak  parasitism  upon 
higher  plants. 

283.  The  reproduction  of  black  molds  is  asexual  and 
sexual.  In  the  asexual  reproduction  (propagation)  the 
mycelium  sends  up  erect  filaments,  which  produce  few  or 
many  separable  reproductive  cells — the  spores.  The 
method  of  formation  of  the  spores  in  a  common  black 
mold  (Mucor)  is  as  follows:  The  vertical  filaments, 
which  are  filled  with  protoplasm,  become  enlarged  at  the 
top,  and  in  each  an  arched  partition  forms,  constitut- 


190  PHYLU.M  IV.     SIPHONOPHYCEAE 

ing  the  so-called  columella.  The  protoplasm  in  the 
enlarged  terminal  segment  (sporangium)  divides  into  a 
large  number  of  minute  masses  (spores)  each  of  which 
surrounds  itself  with  a  cell  wall. 

284.  The  spores  are  set  free  in  different  ways:  in  some 
cases  the  wall  of  the  sporangium  is  entirely  absorbed  by 
the  time  the  spores  are  mature;  in  other  cases  only  por- 
tions of  the  wall  are  absorbed,  producing  fissures  of  va- 
rious kinds.  The  spores  germinate  readily  when  on  or  in 
a  substance  capable  of  nourishing  them,  by  sending  out 
one  or  two  filaments,  which  soon  branch  and  give  rise  to 
a  mycelium.  If  kept  dry,  the  spores  may  retain  their 
vitality  for  months. 

285.  Sexual  reproduction  (generation)  may  take  place 
after  the  production  of  asexual  spores,  but  it  appears  to 
be  of  rare  occurrence  in  our  commonest  species.  Two 
filaments  in  the  air  or  within  the  nutritive  medium,  in 
contact  send  out  small  branches  (here  regarded  as  re- 
duced sexual  organs,  the  one  an  antherid,  and  the  other 
an  oogone) ;  these  elongate  and  become  club-shaped,  and 
at  the  same  time  become  more  closely  united  to  each 
other  at  their  larger  extremities;  a  little  later  a  transverse 
partition  forms  in  each  at  a  little  distance  from  their 
place  of  union;  the  wall  separating  the  new  terminal  seg- 
ments is  now  absorbed,  and  their  protoplasmic  contents 
unite  into  one  common  mass  (the  zygote) ;  the  last  stage 
of  the  process  is  the  secretion  of  a  thick  wall  around  the 
new  mass,  thus  forming  a  zygospore,  i.e.  a  resting  spore, 
which  eventually  germinates  and  sooner  or  later  gives 
rise  to  a  new  plant. 

286.  In  some  Black  Molds  both  gametes  are  formed 
upon  different  branches  of  the  same  mycelium  (homo- 
thallic  forms,  monoecious).  In  many,  however,  the 
plants  are  of  two  kinds  (dioecious),  and  sexual  reproduc- 


INSECT  FUNGI  191 

tion  occurs  only  when  hyphae  of  the  two  kinds  come  into 
contact  (heterothaUic  forms). 

287.  The  Insect-fungi  {Entomophthoraccne)  are  well 
represented  by  the  Fly-fungus  {EntoniophtJiora  muscae)j 
which  in  the  autumn  is  destructive  to  house-flies.  It 
consists  of  small  tubular  coenocytes  which  grow  in  the 
moist  tissues  of  the  fly,  and  at  last  pierce  the 
skin,  producing  minute  terminal  spores,  which 
give  the  fly  a  powdery  appearance.  These 
spores  (called,  also,  conidia)  may  be  seen  as  a 
whitish  halo  surrounding  the  spot  to  which  the 
fly  (now  dead)  has  attached  itself.  Round 
and  thick-walled  resting  spores  (formed  by 
the  union  of  gametes  similar  to  those  of  Black 
Molds)  have  been  observed  in  some  species,  and  may  be 
studied  in  the  Grasshopper  Fungus  {Entomophthora 
grylli),  which  destroys  great  numbers  of  grasshoppers 
every  autumn. 

The  Sexual  Organs  of  the  Water  Molds,  Downy  Mil- 
dews, Black  Molds,  and  Insect  Fungi  show  a  progressive 
degeneration  from  the  typical  structure  occurring  in  the 
Green  Felts.  In  the  Water  Molds  there  is  a  suppression 
of  the  sperms,  the  antherid  protoplasm  being  transferred 
directly  to  the  egg.  This  is  continued  with  little  change 
throughout  the  Downy  ]\Iildews  and  White  Rusts,  which 
being  non-aquatic  could  scarcely  make  use  of  motile 
sperms.  The  sexual  organs  of  the  Black  Molds  are 
apparently  of  the  same  general  type  as  those  of  Water 
Molds  and  Downy  Mildews,  each  being  an  end  cell  cut 
off  from  a  reproductive  filament,  but  in  Black  Molds 
these  filaments  show  little  differentiation.  They  unite 
prematurely,  before  the  oogone  has  developed  an  eg^, 
and  before  the  other  filament  has  developed  its  anthei- 
idial  protoplasm.     They  are  physically  under-developed 


192  PHYLUM  IV.    SIPHONOPHYCEAE 

sexual  organs,  and  are  to  be  regarded  as  mere  vestiges  of 
the  fully  developed  antherids  and  oogones  of  the  Green 
Felts.  They  are  sexual  organs  on  the  road  to  extinction. 
In  the  Insect  Fungi  the  sexual  organs  are  still  more  de- 
generated and  vestigial  in  structure. 

288.  The  commonest  example  of  the   Higher  Tube 
Algae  is  the  little  Bladder  Alga  (Botrydium),  found  on 

»^  moist  ground.      It  is  a  globular  coenocyte 

a  millimeter  or  two  in  diameter,  with  a 
branching  root  below.  When  in  good 
vegetative  condition  it  is  bright  green,  but 
later  it  may  be  dull  red.  It  is  known  to 
Fig     82—    P^opagatc    by    uniciliated    zoospores,   and 

Botrydiuni^ind  thick  wallcd  chlamydosporcs.  Its  genera- 
tion was  long  supposed  to  be  by  the  union 

of  biciliated  isogametes,  but  these  are  now  thought  to 

belong  to  Protosiphon,  a  similar  plant  ^vith  an  unb^anched 

root. 

289.  In  the  shallow  waters  of  the  ocean  there  are 
larger  Bladder  Algae  (Valonia)  that  when  young  are 
single  globose  or  club-shaped  coenocytes,  firmly  rooted 
below.  They  may  reach  several  centimeters  in  height, 
and  ultimately  become  more  or  less  divided 
into  segments.  Their  propagation  and 
generation  appear  to  be  much  like  that 
of  the  little  Bladder  Algae. 

290.  The  Sea  Ferns  (Bryopsis)  are  erect, 
slender,  cylindrical,  single  coenocytes,  rooted 
below,  and  pinnately  branched  above,  and  fig.  83.— Bry- 
look  like  little  trees,  or  fern-leaves.  They  Slaru."^  '^'^" 
generate  by  biciliated  heterogametes.    They 

occur  along  the  shores  of  the  warmer  oceans. 

291.  The   pretty    Sea   Umbrellas  (Acetabularia)    are 
also  erect,  slender,  cylindrical,  single  coenocytes,  rooted 


STONEWORTS 


193 


below;  but  here  the  branches  are  in  one  terminal  whorl 
and  are  united  into  an  umbrella-like  structure.  They 
generate  by  biciliated  isogametes.  They  occur  in  shal- 
low tropical  or  sub-tropical  marine  w^aters. 

292.  In  the  Stoneworts  (Charales)  we  find  the  highest 
development  of  the  coenocytic  structure.  The  plants 
are  erect,  slender,  cylindrical  rows  of  coenocytes,  rooted 
below,  and  bearing  many  whorls  of  free  branches.  The 
stems  are  often  corticated  with  a  parallel  layer  of  smaller 
coenocytes.  They  occur  in  the  fresh  or  brackish  waters 
of  ponds  and  lakes. 

293.  The  generation  of  Stoneworts  is  heterogamous, 
that  is  by  the  union  of  bicihated  sperms,  with  non-ciliated 

eggs.     The  sperms   are   pro- 
duced in  compound  antherids 
which    are    globular     many- 
celled  bodies,  in  the  interior 
of  which  certain  multicellular 
filaments  (the  antherids)  pro- 
duce the  sperms  singly  in  the 
cells.     Each  sperm  is  a  spiral 
thread  of  protoplasm,  provided  with  two  long  cilia  at 
one  end,  by  means  of  which  it  swims  rapidly  through 
the  water. 

294.  The  oogone  is  a  single  cell,  which  soon  becomes 
covered  (corticated)  by  the  growth  from  below  of  a  layer 
of  five  spirally  wound  coenocytes,  which  are  prolonged 
into  a  5-  or  10-cclled  crown.  This  covering,  which  here 
develops  before  fertilization,  is  analogous  to  the  protec- 
tive covering  which  in  Coleochaete,  forms  after  fertiliza- 
tion has  taken  place.  In  the  oogone  is  the  egg,  which  is 
non-ciliated,  and  very  much  larger  than  the  sperms. 

295.  The  sperms  enter  the  opening  at  the  apex  of  the 
oogone  and  one  of  them  entering  the  egg  fertilizes  it. 

13 


Fig.  84.— Chara. 


194  PHYLUM  IV.     SIPHONOPHYCEAE 

The  oogone  and  its  covering  now  become  thicker-walled 
and  constitute  a  spore-fruit.  The  latter  soon  drops  off 
and  falls  to  the  bottom  of  the  water,  where  it  remains  at 
rest  for  a  time  and  later  germinates  by  sending  out  a 
jointed  filament,  which  eventually  gives  rise  to  a  branch- 
ing plant  like  the  original. 

296.  About  IGO  species  of  Stoneworts  are  known,  all 
included  in  the  single  order  Charales.  The  two  f amiUes, 
NiteUaceae  and  Characeae  are  separated  by  the  structure 
of  the  crown,  which  is  10-celled  in  the  former,  and  5- 
celled  in  the  latter.  The  principal  genus  of  the  first 
family  is  Nitella,  and  of  the  second  Chara;  each  contains 
in  this  country  a  dozen  or  more  widely  distributed 
species. 

297.  Summary.  The  attempt  has  been  made  in  the 
foregoing  pages  to  treat  the  coenocytic  plants  in  accord- 
ance with  the  theory  that  they  have  been  derived  from 
the  many-celled  filamentous  algae  of  the  Ulothrix  type 
in  the  Phylum  Chlorophyceae,  where  the  segments  of  the 
filaments  are  true  cells,  each  having  a  single  nucleus. 
And  it  is  regarded  as  probable  that  the  coenocytic  struc- 
ture was  gradually  attained  by  the  formation  of  fewer 
and  fewer  partitions  in  the  succession  of  filamentous 
plants. 

298.  Accordingly  the  Cladophoraceae  are  given  place 
at  the  beginning  of  the  phylum,  and  they  are  regarded 
as  having  given  rise  to  two  general  lines  of  development, 
one  of  which  is  characterized  by  the  retention  of  a  dis- 
tinctly filamentous  structure,  while  in  the  other  the 
coenocyte  undergoes  great  differentiation  into  ''root,'' 
"stem"  and  "leaves."  If  we  designate  these  Hues  by 
their  highest  holophytic  representatives,  we  may  call 
them  (1)  the  Vaucheria  line,  and  (2)  the  Chara  line. 

299.  In  passing  from  Cladophoraceae  to  Vaucheriaceae 


EVOLUTION  OF  SIPHONOPHYCEAE      195 

the  plant  body  has  become  almost  completely  non-septate 
and  the  sexual  reproduction  has  become  heterogamic. 
This  plant  body  and  heterogamic  generation  have  been 
bequeathed  to  the  hysterophj^tes  of  this  line  (Class 
Phycomyceteae) ,  and  both  suffer  marked  degeneration 
in  passing  from  family  to  family. 

300.  So  also  we  may  trace  an  evolutionary  line  from  Cla- 
dophoraceae  to  Valoniaceae  (and  Botrydiaceae),  Bryop- 
sidaceae,  Dasycladaceae,  and  the  Charales,  in  all  of  which 
the  erect,  rooted  and  regularly  branched  plant  body 
becomes  more  and  more  marked.  Here  there  is  again  a 
passage  from  isogamy  to  heterogamy. 

Laboratory  Studies.  Note:  In  addition  to  those  mentioned 
below  many  marine  forms,  as  Codium,  Penicillus,  Halimeda, 
Udotea,  etc.,  occur  in  warm  seas,  and  may  be  studied  with 
profit,  (a)  Collect  a  quantity  of  Water-flannel  (Cladophora) 
and  put  it  into  a  large  dish  of  water,  leaving  it  over  night. 
Next  morning  the  side  of  the  dish  which  is  nearest  to  the  hght 
will  show  a  green  band  at  the  water's  edge,  due  to  the  mjTiads 
of  zoospores  which  escaped  during  the  night.  Mount  a  drop 
of  water  and  search  for  zoospores.  Occasionally  the  escape  of 
zoospores  may  be  seen  by  mounting  a  number  of  filaments  and 
searching  carefully. 

(b)  Collect  a  quantity  of  terrestrial  Green  Felt  (Vaucheria) 
and  preserve  it  in  a  dish  of  water.  After  a  few  hours  a  large 
number  of  zoospores  may  be  observed  collected  at  the  edge  of 
the  water  nearest  to  the  light. 

(c)  Examine  carefully  mounted  specimens  of  the  bright  green 
filaments,  and  look  for  the  thickened  branches  which  produce 
the  zoospores. 

(d)  Select  some  of  the  oldest,  j'cllowish  filaments.  Mount 
and  examine  with  a  low  power  for  the  sexual  organs.  In  col- 
lecting specimens  for  the  study  of  the  sexual  organs  it  is  usually 
necessary  to  take  those  masses  which  arc  yellowish  and  appear 
to  be  dying  or  dead. 

(e)  Kill  a  few  flies  in  strong  alcohol  and  place  them  in  a  dish 
containing  algae  freshly  gathered  from  some  ditch  or  pool. 
After  a  day  or  two  the  flics  will  usually  be  found  to  be  covered 


196  PH\XUM  IV.     SIPHOXOPHYCEAE 

with  whitish  masses  of  radiating  hj'-phae  of  Saprolegnia  or 
related  genera.  Remove  some  of  these  hyphae  and  examine 
for  zoospore  formation.  Somewhat  later  oogones  and  antherids 
may  often  be  found.  A  water  mold  {Saprolegnia  ferax) 
frequently  occurs  upon  the  bodies  of  young  fishes,  especially  in 
fish-hatcheries  where  it  is  occasionally  very  destructive. 

(/)  In  the  Spring  the  leaves  and  stems  of  shepherds'-purse 
and  peppergrass  may  often  be  found  covered  underneath  with 
a  white  mold-like  growth  {Peronospora  parasitica).  Carefully 
scrape  off  a  little  of  this  growth  and  mount  first  in  alcohol, 
afterward  adding  a  little  potassium  hydrate.  The  irregularly 
branching  filaments  will  be  seen  to  bear  here  and  there  white, 
broadly  ellipsoidal  conidia.  Similar  studies  may  be  made  of 
the  Grape-mildew  {Plasmopara  viticola)  on  grape-leaves  in 
autumn,  and  the  Lettuce-mildew  {Bremia  lactucae)  on  cultivated 
and  wild  lettuce  from  spring  to  autumn. 

(g)  Make  very  thin  cross-sections  of  a  leaf  affected  with  a 
Downy  Mildew,  when  the  latter  has  passed  the  period  of  its 
greatest  vegetative  activity.  Mount  in  alcohol  (to  drive  out 
air-bubbles),  then  add  potassium  hj'drate,  and  look  for  the 
resting-spores,  which  in  some  species  are  of  a  dark  brown  color. 

(h)  White  Rusts  occur  on  man}?-  plants:  one  {Albugo  Candida) 
on  shepherd's-purse,  peppergrass,  radish,  etc.;  another  {A. 
hliti)  on  Amaranthus;  and  another  (.4.  portulacae)  on  purslane. 
For  conidia  make  very  thin  cross-sections  of  leaves,  through  a 
white-rust  spot,  and  mount  as  above.  The  resting  spores 
(which  are  dark  brown)  are  easily  obtained  in  the  leaves  of 
Amaranthus  and  purslane  and  in  the  distorted  stem  of  the 
radish. 

{i)  In  the  study  of  Black  Molds  it  is  mostly  necessary  to 
make  use  of  alcohol  for  freeing  the  specimens  of  air;  afterward 
they  usually  require  to  be  treated  with  a  dilute  alkah  (as  a 
weak  solution  of  ammonia  or  potassium  hydrate),  which 
causes  the  filaments  to  swell  up  to  their  original  proportions. 

{j)  Cut  a  lemon  in  two,  and,  squeezing  out  most  of  the  juice, 
expose  the  two  halves  to  the  air  af  an  ordinary  laboratory  or 
living-room  for  a  few  days,  when  various  molds  will  begin  to 
develop.  Under  favorable  circumstances  Black  Mold  (Mucor) 
will  predominate.  It  can  be  told  by  its  dark  color  and  the 
minute  round  black  sporangia  on  the  ends  of  the  erect  filaments. 


LABORATORY  STUDIES  197 

Mount  a  few  filaments  (as  directed  in  i  above)  and  examine 
filaments,  sporangia,  and  spores. 

{k)  Moisten  a  piece  of  bread  and  then  sow  here  and  there  on 
its  surface  a  few  spores  of  Black  Mold;  cover  with  a  tumbler  or 
bell  glass.  In  a  few  hours  a  new  crop  of  Black  Mold  will  Ijogin 
developing.  The  nutritive  mycelium  may  be  studied  by 
teasing  out  small  bits  of  the  newly  infected  bread. 

(0  Place  several  clean  glass  slides  in  contact  with  a  culture  of 
black  mold,  as  described  in  (^•).  By  removing  these  at  different 
times  the  various  stages  of  growth  of  the  mold  may  be  easily 
studied. 

{m)  Collect  a  number  of  large  fleshy  fungi  (Boletus,  Lactaria, 
Agaricus,  etc.)  and  place  under  bell  jars  for  a  couple  of  days. 
Usually  a  cream-colored  mold  {Sporodinia  grandis)  will  begin 
to  develop  upon  some  of  these.  Transfer  it  to  pieces  of  bread 
as  in  (A-)  and  study  in  a  similar  way.  After  a  few  days  the 
zygospore  formation  will  be  observed,  as  this  species  is  homo- 
thallic. 

{n)  In  the  latter  part  of  summer  and  in  the  autumn  examine 
the  dead  flies  which  adhere  to  windowpanes,  door-casings,  and 
especially  to  wires  and  strings  hanging  from  the  ceiling.  '  The 
whitish  powder  around  the  fly  will  indicate  the  presence  of  the 
Fly-fungus  {Entomophthora  muscae).  Mount  some  of  this 
white  powder  in  water  and  examine  under  a  high  power.  Tear 
out  small  bits  of  the  distended  abdomen  of  the  fly,  and  examine 
for  internal  portions  of  the  parasite. 

(o)  In  the  autumn  look  for  dead  grasshoppers  attached  to  the 
tops  of  weeds  and  grasses.  Examine  their  interior  tissues  for 
thick- walled  resting  spores  of  Entomophthora  grylli. 

(p)  In  damp  weather  in  the  summer  look  for  Botrydium  on 
the  hard,  smooth  ground  of  unused  paths.  It  often  appears 
on  compact  soil  in  greenhouses  in  the  winter. 

iq)  Specimens  of  Valonia,  Bryopsis,  Caulcrpa  and  Acetabu- 
laria  may  be  obtained  of  dealers  in  laboratory  material  for 
study  and  examination. 

(r)  Search  the  sandy  margins  of  ponds,  lakes,  and  slow  streams 
for  Stoneworts  (Charales).  They  are  generally  found  in  water 
from  a  few  centimeters  to  one  or  two  meters  in  depth.  Pre- 
serve such  specimens  temporarily  in  water  which  is  frequently 
changed,  but  for  future  use  preserve  in  alcohol.  Study  as 
follows. 


198  PHYLUM  IV.    SIPHONOPHYCEAE 

(.s)  INIoimt  carefully  a  considerable  portion  of  a  fresh  plant, 
and  examine  its  structure  under  a  low  power.  Note  that  in 
some  species  the  stem  is  composed  of  a  row  of  large  coenocytes 
surrounded  by  a  coat  of  smaller  ones.  Look  for  the  rapid 
movement  of  protoplasm  which  is  so  marked  in  these  plants. 

(0  Mount  several  spore-fruits  in  various  stages  of  develop- 
ment. Note  the  covering  layer  of  spirally  coiled  cells  surround- 
ing the  oogone  (in  young  specimens)  or  the  resting  spore  (in 
older  specimens). 

(u)  Mount  several  full-grown  compound  antherids.  Care- 
fully crush  them  and  look  for  sperms,  which  are  produced  in 
chains  of  cells  (antherids). 

LITERATURE  OF  SIPHONOPHYCEAE 

Frank  S.  Collins,  The  Green  Algae  of  North  America,  Tufts 
College,  1909. 

G.  S.  West,  A  Treatise  on  the  British  Fresh-water  Algae,  Cam- 
bridge, 1904. 

F.  E.  Clements,  The  Genera  of  Fungi,  Minneapolis,  1909. 

W.  Migula,  Die  Characeen,  etc.,  in  Rabenhorst's  Kryptoga- 
men  Flora  von  Deutschland,  Oesterreich  u.  d.  Schweiz,  Vol.  V, 
Leipzig,  1897. 


CHAPTER  XI 
PHYLUM  V.     PHAEOPHYCEAE 

THE  BROWN  ALGAE 

301.  The  Brown  Algae  which  are  almost  wholly  marine 
plants  of  shallow  waters,  numbering  about  1000  species, 
are  all  truly  cellular,  and  range  from  small  filamentous 
few  celled  plants,  to  large  massive  organisms  differenti- 
ated into  roots,  stems  and  leaves.  They  are  brown- 
green  in  color,  and  contain  other  coloring  matters  in  their 
cells  in  addition  to  chlorophyll.  They  are  propagated 
mostly  by  laterally  biciliated  zoospores,  and  generated 
in  the  lower  families  by  isogametes,  and  in  the  higher 
famiUes  by  heterogametes,  their  union  in  all  cases  pro- 
ducing a  simple  zygote.  The  gradations  in  the  sexual 
union  of  the  gametes  include  (1)  biciliated  isogametes, 
(2)  biciliated  heterogametes,  (3)  biciliated  for  uniciliated) 
sperms  and  non-ciliated  eggs. 

302.  In  this  phjdum  the  dominant  feature  is  the  addi- 
tion of  the  brown  pigment,  phycophaein,  to  the  chloro- 
phyll of  the  cells.  With  this  character  must  be  associated 
the  typically  motile,  usually  biciliated  gametes,  produc- 
ing simple  zygotes  upon  uniting,  and  the  rooted  plant 
body  (from  filamentous  and  small,  to  massive  and 
large.) 

303.  Brown  Algae  probably  originated  in  the  vicinity 
of  Ulotrichaceae  in  the  Chlorophyceae.  The  phylum 
constitutes  a  ''side  line"  diverging  from  the  main  evolu- 
tionary stem  or  current. 

199 


200  PHYLU:M  \.     PHAEOPHYCEAE 

304.  Among  the  commonest  of  the  smaller  Brown  Algae 
are  the  species  of  Ectocarpus  in  which  the  plant  body  is 
composed  of  simple  or  branched  filaments  which  may 

attain  a  length  of  many  centimeters.  They 
are  firmly  rooted  below,  and  their  tufted 
filaments  float  as  dark  brown  masses  in  the 
tide  currents  near  the  shore.  They  are 
propagated  by  zoospores  produced  in  one- 
celled  sporangia  which  occur  on  the  sides 
Ectocafpus.  of  the  filaments.  These  zoospores  are 
oval,  pointed  anteriorly,  and  have  two 
long  cilia  which  are  attached  near  together  at  one  side. 
Generation  takes  place  by  the  union  of  isogametes,  re- 
sembling the  zoospores,  but  originating  in  many-celled 
sporangia  (gametangia)  also  occurring  on  the  sides  of  the 
filaments.  This  union  takes  place  in  the  water  after 
both  gametes  have  escaped  from  the  sporangia,  and  it 
results  in  the  formation  of  a  zygote,  which  soon  germi- 
nates and  gives  rise  to  a  new  plant. 

305.  The  Kelps  (Laminariaceoe)  while  large  massive 
plants  are  still  of  a  low  type.  In  the  Flat  Kelps,  or 
Devil's  Aprons  (Laminaria),  there  is  a  stout  stem  a  cen- 
timeter or  so  thick,  and  a  decimeter  to  nearly  a  meter 
long,  firmly  rooted  below,  and  flat- 
tened into  a  broad  'Ueaf"  above. 
The  whole  plant  may  be  a  meter  or 
even  several  meters  in  length,  and 
the  ''leaf"  a  few  centimeters  to  half 
a  meter  in  breadth.  On  the  sur- 
face of  the  ''leaf"  there  develop  """•  s^-^-^^-^"- 
patches  of  1-celled  sporangia  that  produce  zoospores 
like  those  in  Ectocarpus.  Gametes  are  not  certainly 
known  to  occur  in  the  Kelps. 

306.  Other  kelps  that  are  common  on  the  Atlantic  or 


KELPS  201 

Pacific  coasts  are  the  Sea  Girdle  (Cymathere)  with  a 
narrow  beautifully  ribbed  "  leaf" ;  the  Sea  Tree  (Lessonia) 
with  a  stout  branching  stem  bearing  many  small  leaves; 
the  Sea  Palm  (Postelsia)  with  an  unbranched  stem  bearing 
a  tuft  of  leaves  at  the  top;  the  Bladder  Kelp  (Nereocystis) 
with  a  long,  cord-like  stem,  often  10  to  15  meters  long  and 
bearing  an  air  bladder  at  the  top,  to  which  is  attached  a 
tuft  of  large  leaves;  the  Giant  Kelp  (Macrocystis)  with  a 
long,  slender,  cord-like  stem,  sometimes  50  to  75  meters 
long  and  bearing  a  row  of  large  leaves  toward  its  extrem- 
ity, each  with  a  basal  air  bladder;  the  Leafy  Kelp  (Egre- 
gia)  with  a  fiat  stem  which  bears  innumerable  lateral  leaf- 
lets and  air  bladders. 

307.  The  highest  of  the  Brown  Seaweeds  are  the  Rock- 
weeds  and  Gulf  weeds  (Fucales)  in  which  the  plant  body  is 
of  medium  size  (usually  from  a  decimeter 
to  a  meter  in  length),  rooted  below,  and 
massive  and  branching  above.  Their 
tissues,  too,  show  a  considerable  differ- 
entiation; the  cells  are  arranged  in  cell- 
masses,  and  these  are  differentiated  into 
several  varieties  of  parenchyma,  and  other 
tissues  approaching,  in  some  instances,  to  the  condition 
which  prevails  in  higher  plants.  Some  species  develop 
air  bladders  in  their  tissues. 

308.  With  the  foregoing  there  is  found  a  marked  differ- 
entiation of  portions  of  the  plant  ])ody  into  general  re- 
productive organs,  analogous  to  the  floral  branches  of 
higher  plants.  The  sexual  organs  are  developed  upon 
modified  l^ranches,  which  differ  more  or  less  in  shape  and 
appearance  from  those  destitute  of  such  organs. 

309.  In  all  Rockweeds  the  asexual  reproduction 
("propagation")  has  been  suppressed,  the  emphasis  l^eing 
placed  upon  the  sexual  reproduction  ("generation"). 


Fig.  S7. — Fucus. 


202  PHYLUM  V.     PHAEOPHYCEAE 

310.  In  common  Rockweeds  (Fucus)  of  the  seashore 
the  sexual  organs  are  found  in  the  thickened  ends  of  the 
lateral  branches.  The}^  occur  on  the  walls  of  cavities 
(conceptacles),  which  are  spherical,  with  a  small  opening 
at  the  top.  The  conceptacles  are  at  first  portions  of  the 
general  surface,  and  afterward  become  depressed  and 
walled  in  by  the  overgrowth  of  the  surrounding  tissues; 
they  are  thus  in  reality  portions  of  the  general  surface. 

311.  The  walls  of  the  conceptacles  are  clothed  with 
pointed  hairs,  which  in  some  species  project  through  the 
opening,  and  among  these  are  found  the  sexual  organs. 
The  antherids  are  produced  as  lateral  ])ranches  of  hairs; 
each  antherid  is  a  thin-walled  structure  containing  a 
large  number  of  biciliatecl  sperms,  which  escape  by  the 
rupture  of  the  surrounding  wall.  Before  rupturing, 
however,  the  antherids  detach  themselves  and  float  in  the 
water  with  their  contained  sperms. 

312.  The  oogone  is  a  globular  or  ovoid  short-stalked 
body  containing  eight  eggs.  These  escape  from  the 
oogone  and  float  out  through  the  opening  of  the  concep- 
tacle,  into  the  open  water.  The  sperms,  which  are  lib- 
erated at  about  the  same  time,  gather  around  the 
inactive  eggs  in  great  numbers,  and  by  the  vigor  of 
their  movements  sometimes  actually  give  them  a  rotary 
motion.  Fertilization  results  from  the  union  of  one  of 
these  sperms  with  the  egg,  the  zygote  thus  produced 
secreting  a  Avail  of  cellulose  about  itself. 

313.  In  germination  the  zj-gote  lengthens  and  under- 
goes division  into  numerous  cells;  at  the  same  time  it 
elongates  below  into  root-like  processes,  which  serve  to 
hold  fast  the  new  plant. 

314.  In  the  nearly  related  Gulfweeds  (Sargassum)  the 
plant  body  is  composed  of  a  distinct  stem,  rooted  below, 
and  bearing  leaves  above.     The  stem  bears  also  many 


GULFWEEDS  203 

stalked  air  bladders  which  ])uoy  up  the  plant  when 
rooted,  and  float  it  when  torn  free.  The  short,  thickened, 
elontrated  and  clustered  axillary  branches  (receptacles) 
which  contain  the  conceptacles  ma}'  be  dis- 
tinguished easil}^  from  the  spherical  air  l^lad- 
ders.  There  are  many  species,  one  of  which 
(Sargassum  vulgare)  is  common  along  our 
eastern  coast  as  a  low-tide  plant,  half  a  meter 
to  a  meter  long.      Another  smaller  species        Fig.  88. 

/-»  •/•  \    n  •  '111  Sargassum. 

{bargassum  oacciferum)  iloats  m  considerable 
quantities  in  the  so-called  ''Sargasso  Sea"  of  the  central 
Atlantic  Ocean.     Its  proper  home  is  in  the  West  Indian 
region,  where  it  grows  attached  to  rocks. 

Laboratory  Studies.  Probably  the  best  Brown  Algae  for  the 
beginner  to  take  up  are  Ectocarpus,  Laminaria,  and  Fucus. 

(a)  Good  material  of  Ectocarpus  for  study  may  be  obtained 
of  dealers  in  laboratory  supplies.  The  specimens  should  be 
examined  with  reference  to  tlic  general  form  and  appearance  of 
the  plant  body,  and  especially  for  the  1-celled,  and  the  many- 
celled  sporangia. 

(/;)  Where  fresh  material  cannot  be  secured,  the  Kelps  may 
be  studied  very  well  from  preserved  specimens,  which  can  also 
be  obtained  from  dealers  in  botanical  supplies. 

(c)  Study  the  tissues  of  Laminaria  and  other  Kelps  in  cross 
and  longitudinal  sections. 

(d)  Make  sections  through  the  fruiting  j)atc]ies  and  examine 
the  sporangia  and  ''paraphyses,"  that  is,  the  elongated, 
intervening  protective  cells. 

(e)  It  is  helpful  to  have  jars  of  other  Kelps,  as  Sea  Palms, 
Bladder  Kelj)s,  Giant  Kelps,  Leafy  Kelps,  etc.,  for  macroscopic 
observation. 

(/)  Secure  specimens  of  Rockweeds,  fresh,  alcoholic,  or  dry. 
Fresh  ones  may  easily  be  found  along  the  beach  of  the  ocean 
after  a  storm.  AlcohoHc  and  dry  specimens  and  even  living 
material  can  easily  be  procured  by  purcliase  or  exclianpe. 
Make  thin  cross-sections  through  the  conceptacles  in  the  thick- 
ened ends  of  the  branchlets.     When  mounted  in  water,  even  the 


204  PHYLUIM  V.     PHAEOPHYCEAE 

sections  from  the  drj"  specimens  will  frequently  show  the  sexual 
organs  quite  well.  It  must  be  remembered  that  some  species 
are  dioecious,  i.e.  have  the  antherids  on  one  plant  and  the 
oogones  on  another. 

(g)  Make  very  thin  cross  and  longitudinal  sections  of  differ- 
ent portions  of  the  plant  bod}',  and  study  the  tissues.  Note 
particularly  the  boundary  tissue  (epidermis),  and  the  cells 
constituting  the  mid-ribs  and  harder  portions  of  the  stems  and 
leaves. 

(h)  Secure  in  like  manner  specimens  of  Gulfwced,  and  make 
macroscopic  examination  of  the  plant  body,  then  if  there  is 
time  available  make  cross-sections  of  the  air  bladders  and  the 
receptacles. 

LITERATURE  OF  PHAEOPHYCEAE 

George  Murray,  An  Introduction  to  the  Study  of  Seaweeds, 

London,  1895. 
G.  B.  De  Toni,  Sylloge  Algarum,  vol.  Ill,  Padua,  1895. 
W.  G.  Farlow,  Marine  Algae  of  New  England  and  Adjacent 

Coast,  Washington,  1881. 


CHAPTER  XII 

PHYLUM  VI.     RHODOPHYCEAE 

THE  RED  ALGAE 

315.  The  Red  Algae  are  almost  wholly  marine  plants, 
in  structure  ranging  from  small,  simple,  cellular,  attached 
filaments  to  stout,  massive,  rooted  plants  which  may 
attain  considerable  dimensions  (half  a  meter  or  more). 
The  smaller  plants  are  often  diffusely  and  beautifully 
branched  into  quite  intricate  patterns,  rising  from  a 
short  basal  stem  which  is  rooted  below,  while  in  the 
larger  forms  there  may  be  a  thick,  rooted  stem 
which  bears  one  or  more  flat  leaves  above. 

316.  The  cell  walls  of  the  Red  Algae  are 
more  or  less  gelatinous  in  nature  and  swell 
greatly  in  fresh  water,  even  dissolving.  The 
cells  usually  are  connected  with  one  another 
by  visible  openings  in  their  walls,  so  that  the 
protoplasm  is  continuous  from  cell  to  cell. 

317.  The  cells  contain  chloroplasts,  but  their  green 
color  is  masked  by  the  presence  of  a  red  or  purple 
coloring  matter  (phycoerythrin)  and  sometimes  a  blue 
coloring  matter  (phj^cocyanin),  so  that  the  plants  appear 
red  or  purple,  instead  of  green,  although  in  fact  they 
are  green;  but  lit  must  not  be  overlooked  that  a  few 
species  are  parasitic,  and  therefore  devoid  of  coloring 
matter! 

318.  The  Red  Algae  are  propagated  by  non-ciliated, 
naked  cells  which  are  separated  from  the  plant,  either 

205 


206  PHYLUM  VI.     RHODOPHYCEAE 

singly  C'monospores")  or  in  groups  of  fours  ('Hetra- 
spores");  these  float  away  and  on  germination  give  rise 
to  new  plants.  They  are  generated  heterogamically  by 
the  union  of  non-motile  sperms  with  enclosed  eggs, 
usually  resulting  in  the  growth  of  branching,  sporebearing 
filaments,  mostly  covered,  and  constituting  a  primitive 
many-spored  fruit  (^'cystocarp"). 

319.  In  those  species  (by  far  the  greater  number  of  the 
Red  Seaweeds)  in  which  tetraspores  are  produced,  these 

give  rise  to  the  sexual  plants  which 
are  mostly  dioecious.  The  carpospores 
from  the  latter  give  rise,  in  their  turn, 
to  the  tetrasporic  plants.  The  nuclei 
of  the  latter  possess  the  diploid  number 

FiQ.  90. — Tetraspores.        p       ^  ±^  r    j.i        j* 

of  chromosomes;  those  oi  the  former 
the  haploid  number,  the  reduction  of  chromosomes  tak- 
ing place  during  the  divisions  leading  to  the  production 
of  the  tetraspores. 

320.  Here  the  dominant  characters  are  the  reddish 
pigment  added  to  the  chlorophyll  of  the  cells,  and  the 
development  of  the  zygote  into  a  sporiferous,  usually 
covered,  tissue  (the  spore  fruit;  cystocarp).  The  im- 
portant secondary  characters  are  the  definite  and  final 
attainment  of  heterogamy,  and  the  mostly  symmetrically 
branched  and  basally  rooted  plant  body. 

For  the  most  part  the  Red  Algae  grow  at  very  consider- 
able depths  in  the  waters  of  the  ocean,  although  a  few 
occur  near  the  shore,  and  a  very  few  live  in  fresh  water. 
They  are  more  abundant  in  the  warmer  waters,  and  be- 
come less  frequent  as  we  go  toward  the  poles.  The 
number  of  known  species  is  about  three  thousand. 

321.  This  phylum  as  a  whole  is  poorly  understood. 
Very  little  consideration  has  been  given  to  the  physical 
modification  these  plants  have  suffered  through  living 


RED  SEAWEEDS  207 

(1)  at  such  depths  (where  the  Ught  is  greatly  modified), 
and  also  (2)  in  waters  of  such  considerable  salinity.  It 
is  probal^le  that  this  modification  has  masked  their  true 
relationship  to  other  plants,  as  well  as  to  one  another. 

322.  One  of  the  lowest  of  the  Red  Algae  is  the  common 
"Laver"  (PorphjTa),  of  the  class  bangioideap:,  of  all 
coasts,  in  which  the  erect,  deep  purple,  leaf-like,  and 
basally  rooted,  plant  body  is  composed  of  a  single  layer 
of  cells.  They  propagate  by  monospores  borne  in  the 
cell  layer.  In  their  very  simple  generation  certain  cells 
of  the  cell  layer  divide  into  non-ciliated  sperms,  while 
others  ])ecome  very  slightly  modified  into  oogones,  each 
containing  a  single  egg.  The  latter  is  fertilized  by  the 
entrance  of  the  sperm  through  an  opening  in  the  cell 
wall,  after  which  the  zygote  develops  into  usually  eight 
spores.     The  fruit  is  thus  of  very  simple  structure. 

323.  In  Nemalion  (which  with  the  succeeding  plants 
belongs  to  the  class  florideae),  a  branching,  filamentous 
marine  Red  Alga,  the  clustered  antherids 
produce  small  spherical,  non-ciliated 
sperms.  The  oogone  is  prolonged  into  a 
slender  structure,  the  trichogyne,  and  to 
this  latter  the  sperm  adheres  and  fertilizes 
the  egg.  After  fertilization  the  egg  divides, 
and  each  new  cell  sends  out  short  crowded 
branches  which  bear  terminal  spores.  Here  no  protec- 
tive envelope  covers  the  spores,  the  fruit  being  very 
simple.     Asexual  reproduction  is  not  known. 

324.  Here  may  ])e  noted  briefly  the  Corallines  (('oral- 
lina)  which  are  filamentous  Red  Algae  which  become  so 
heavily  coated  with  lime  as  to  efYectually  hide  their  cells. 
This  lime  coating  is  like  an  ancient  coat  of  mail  with  its 
flexible  joints  at  intervals.  The  antherids  and  oogones 
are  in  separate  terminal  cup-shaped  structures,  those  con- 


208  PHYLUM  VI.     RHODOPHYCEAE 

taining  the  oogones  becoming  the  fruit  after  fertilization. 
Tetraspores  occur  in  similar  cup-shaped  structures. 

325.  Polysiphonia  contains  plants  in  Avhich  the  branch- 
ing, filamentous  plant  body  is  composed  of  more  than  one 
row  of  cells,  usually  of  a  central  row  surrounded  by  an 
outer  layer,  completely  covering  it.  These  shallow- 
water  plants  are  often  of  marked  beauty  both  in  struc- 
ture and  coloring.  The  tetraspores  are 
produced  in  unmodified  or  slightly  swollen 
branches,  and  originate  within  the  tissues, 
but  with  the  increase  in  size  of  the  tetra- 
sporangia  they  eventually  reach  the  surface 
and  sUp  out  as  large,  deeply  colored  naked 

Polysiphonia.  ccUs.  The  spccial  antheridial  branches 
consist  of  a  central  axis  with  numerous 
short,  crowded,  radiating  branchlets  whose  extremi- 
ties (antherids)  abstrict  the  naked,  colorless  sperms. 
The  oogone  possesses  a  trichogyne,  and  is  surrounded  by 
a  few  protective  cells.  The  sperms  carried  by  currents 
of  water  come  in  contact  with  the  trichogyne,  and 
attach  themselves  to  it  and  form  cell  walls.  The  nucleus 
of  one  passes  into  the  trichogyne,  and  unites  with  that  of 
the  oogone.  The  oogone  now  fuses  (for  nutritive  pur- 
poses, as  there  are  no  nuclear  fusions)  with  a  large  nearby 
cell  (the  auxiliary  cell)  into  which  the  zygote  nucleus 
passes,  and  from  which  arise  the  filaments  which  produce 
the  carpospores.  In  the  meantime  the  surrounding 
cells  produce  an  urn-shaped  structure  (pericarp)  w^th 
an  opening  at  the  top  from  which  the  liaked  carpospores 
escape  at  maturity. 

326,  Irish  Moss  (Chondrus)  is  so  easily  obtained  at  the 
apothecaries  that  it  may  well  be  cited  as  one  with  a 
parenchymatous,  much  branched  plant  body.  The 
oogones  and  afterward  the  spore  fruits  are  immersed  in 


RED  SEAWEEDS  209 

the  substance  of  the  plant  body.  The  plants  are  col- 
lected, washed  and  dried  and  so  preserved  for  human  food 
(blanc  mange)  and  especially  as  a  food 
for  convalescents.  The  structure  of  Cal- 
lymenia  is  similar  to  that  of  Chondrus. 

327.  Among  the  very  commonly  col- 
lected Red  Algae  on  either  coast  are  speci- 
mens of  Plocamium  remarkable  for  the 
beauty  of  its  color  and  the  regularity  of 
its  branching. 

Laboratory  Studies,  (a)  It  is  better  for  the  student  to 
stud}^  the  li\'ing  plants  of  this  phjdum  at  the  seashore,  but  the 
beginner  should  not  fail  to  make  a  study  of  such  specimens  as 
may  be  accessible.  Specimens  for  the  study  of  structure  should 
be  preserved  in  alcohol  or  formalin,  using  sea-water  instead  of 
fresh  water.  However,  much  may  be  made  out  by  the  careful 
examination  of  dried  specimens  which  may  be  obtained  from 
dealers.  Red  Seaweeds  may  often  be  obtained  ''in  the  rough'* 
which  can  be  moistened  and  then  pressed  out  and  dried  for 
study.  Such  material  will  often  yield  quite  good  si)ecimens. 
Good  mounted  microscopic  specimens  may  sometimes  be  ob- 
tained showing  the  structure  of  the  plant  as  well  as  of  the  sexual 
and  asexual  reproductive  organs. 

(b)  Make  careful  microscopical  examination  of  Poly- 
si})honia  using  alcoholic  or  formalin  material.  Such  mounts 
should  be  made  in  sea-water  or  a  3  per  cent,  salt  solution  to 
avoid  the  swelling  of  the  cell  walls.  In  the  course  of  the  study 
the  following  should  be  noted:  (i)  the  cellular  structure  of  the 
plant  body,  (ii)  the  tetraspores,  (iii)  the  antherids,  (iv)  the 
oogones  (difficult  to  find),  (v)  the  cystocarps  with  their  sj^orcs 
(carposporos).  The  closely  related  Dasya  may  be  substituted 
for  Polysii)honia. 

(c)  Study  the  tissue  of  Chondrus. 

(d)  Dried  specimens  of  some  or  all  of  the  following  genera, 
mounted  on  heavy  white  paper,  or  cardboard,  should  be 
available  for  macroscopic  examination. 

Porphvra,   ]5atrachospermum,   Corallina,    Grinnellia,    Xito- 
phyllum,   Polysiphonia,   Dasya,   Chondrus,   Callophyllis,   and 
Plocamium. 
u 


210  PHIlTLUM  VI.     RHODOPHYCEAE 

LITERATURE  OF  RHODOPHYCEAE 

George  Murray,  An  Introduction  to  the  Study  of  Seaweeds, 

London,  1895. 
G.  B.  De  Toxi,  Sylloge  Algarum,  Vol.  IV,  Padua,  1897-1905. 
W.  G.  Farlow,  Marine  Algae  of  New  England  and  Adjacent 

Coast,  Washington,  1881. 


CHAPTER  XIII 
PHYLUM  VII.     CARPOMYCETEAE 

THE  HIGHER  FUNGI 

328.  The  plants  here  brought  together  are  all  hystero- 
phytes,  being  destitute  of  chlorophyll  or  any  other  simi- 
lar coloring  matter  with  physiological  significance.  In 
accordance  with  the  theory  underlying  the  treatment  of 
all  plant  phyla  in  this  book  these  hysterophytes  must 
have  been  derived  from  some  of  the  preceding  holophytes, 
and  it  seems  most  probable  that  they  came  from  the  plants 
in  the  phylum  immediately  preceding  this  one.  In  other 
words,  it  is  here  assumed  that  the  Higher  Fungi  arc  allied 
in  structure  to  the  Red  Algae,  and  that  the  striking  differ- 
ences between  them  are  correlated  principally  with  the 
change  from  the  holophytic  to  the  hysterophytic  habit, 
but  it  must  be  remembered  also  that  the  Red  Algae  arc 
aquatic  plants,  while  nearly  all  the  Higher  Fungi  have 
adapted  themselves  to  terrestrial  or  aerial  (non-aquatic) 
conditions. 

329.  The  Higher  Fungi  may  be  characterized  as  fol- 
lows: They  are  filamentous  plants,  whose  cells  are  always 
without  chlorophyll.  Visible  protoplasmic  connections 
between  cell  and  cell  are  common.  The  filaments  are 
mostly  isolated,  but  sometimes  they  are  compacted  into 
parenchymatous  masses,  yet  in  few  cases  is  there  a  con- 
spicuous plant  body  comparable  to  the  body  of  the  re- 
lated chlorophyll-bearing  plants.  This  obsolescence  of 
the  plant  body  results  from  the  abandonment  of  tlie  holo- 
phytic  habit,  which   has  rendered    chlorophyll-bearing 

211 


212  PHYLUM  VII.     CARPOMYCETEAE 

cells  unnecessary.  The  vestiges  of  the  plant  body  are 
present  mainly  as  root-like  absorbing  organs,  which  di- 
rectly bear  the  reproductive  structures. 

330.  The  Higher  Fungi  are  propagated  mainly  by  (1) 
the  separation  of  special  terminal  cells  (conidia),and  (2) 
the  separation  of  considerable  fragments  of  the  original 
plant  body.  Zoospores  are  unknown  in  this  phylum. 
They  generate  by  the  union  of  the  protoplasm  of  an  an- 
therid  with  the  egg  in  an  oogone,  resulting  in  the  produc- 
tion of  a  spore-fruit  (sporocarp)  consisting  of  (1)  sporog- 
enous  and  (2)  sterile  tissues.  In  the  fertilization  of  the 
egg  no  instance  is  known  of  the  production  of  motile 
sperms. 

331.  Because  of  the  reduction  of  the  plant  body  the 
spore-bearing  structures,  asexual  and  sexual,  appear  to 
be  relatively  large.  Moreover,  because  of  the  dependent 
habit  of  the  Higher  Fungi  it  is  necessary  that  many  spores 
should  be  produced,  so  that  correlated  with  their  depend- 
ence is  the  great  increase  in  the  number  of  spores,  and  the 
size  of  the  spore-bearing  structures.  Thus  it  happens 
that  in  many  cases  there  is  an  actual  increase  in  the  size 
and  development  of  the  spore-bearing  structures,  espe- 
cially of  the  spore  fruits.  In  many  Higher  Fungi  no 
sexual  organs  have  been  found,  and  it  is  thought  that  they 
may  have  disappeared  through  the  degradation  of  the 
plant  body. 

332.  This  phylum  contains  about  64,000  known  spe- 
cies, and  these  may  be  arranged  under  three  classes,  with 
an  additional  group  of  poorly  understood,  and  unassorted 
plants. 

A.  Spore  fruits  containing  one  or  more  asci,  with  ascospores. 

Class  ASCOSPOREAE. 

B.  Spore  fruits  containing  one  or  more  basidia,  with  basidio- 
spores.  Class  Basidiosporeae. 


ASCOSPHOREAE  213 

C.  Spore  fruits  much  reduced,  containing  teliospores. 

Class  Teliosporeae. 

D.  Asci,   basidia  or  teliospores  unknown  (artificial  group). 

Fungi  Imperfecti. 


Class  14.     ASCOSPOREAE.     The  Ascus  Fungi. 

333.  This  large  class  includes  chlorophyll-less  plants 
which  differ  much  in  size  and  appearance,  but  which  agree 
in  producing   their  fruit-spores  (carpo- 

spores)  in  sacs  (asci),  and  because  they 
are  in  sacs  they  are  called  sac-spores  or 
ascospores.  These  spore-bearing  sacs 
(singular,  ascus;  plural,  asci)  are  end- 
cells  in  the  sporogenous  tissue  of  the 
fruit   of   the  fungus,  and  they  tend  to     Fio.  94.— Deveiop- 

.  .  r  'f  ^     •  mcnt     of     asci    and 

develop  m  a  layer  of  uniform  height —  ascospores. 
the  so-called  ''h3^menium." 

334.  The  sexual  organs  where  known  consist  of  oogones 
and  antherids,  and,  after  fertilization,  produce  a  spore- 
fruit  (sporocarp)  which  includes  the  sacs  and  sac-spores 
(ascospores).  The  most  common  number  of  ascospores 
is  eight  in  each  ascus;  but  it  sometimes  exceeds,  and  fre- 
quently falls  short,  of  this  number,  there  being  sometimes 
no  more  than  one  or  two. 

335.  In  addition  to  the  ascospores  there  are  generally 
one  or  more  other  kinds  of  spores  which  are  developed 
asexually.  Some  of  these  are  doubtless  to  be  regarded  as 
the  equivalents  of  the  conidia  of  the  lower  groups,  and 
accordingly  will  be  so  named  here. 

336.  The  Ascus  Fungi  include  about  29,000  species, 
representing  15  orders  and  80  families.  In  the  treat- 
ment hero  a  selection  has  been  made  of  representative 
forms. 


214  PHYLUM  VII.     CARPOMYCETEAE 

The  Disk  "Lichens"  (ORDER  DISCOLICHENES) 

337.  The  primitive  Asciis  Fungi  (Ascosporeae)  appear  to 
have  been  parasitic  on  small,  green  algae  (myxophyceae 
and  khlorophyceae),  and  indeed  this  may  have  first 
taken  place  in  the  water.  It  is  known  that  some  of  the 
proper  Red  Algae  are  parasitic,  and  the  view  here  taken  is 
t  hat  in  the  Disk  Lichens  we  have  a  group  of  plants  in  which 
the  parasitism  has  gone  further,  and  has  resulted  in  so 
great  a  modification  of  the  plant  body  as  to  place  them  in 
another  phylum. 

338.  The  Disk  Lichens  abound  almost  everywhere — 
on  tree-trunks,  rocks,  old  roofs,  and  in  many  regions  upon 
the  ground.  They  are  for  the  most  part  of  a  greenish- 
gray  color,  and  hence  are  often  called  ''Gray  Mosses.'' 
Other  colors,  as  black,  purple,  yellow,  and  white,  are  also 
common. 

339.  The  plant-body  of  a  Disk  Lichen  is  composed  of 
jointed,  branching,  colorless  filaments,  similar  to  those  in 

-TTTTv-r-T-r-r  the  other  fungi,  but  usually  more  or  less 
compacted  together  into  a  thallus,  or  even 
a  branching  stem.  They  obtain  their 
nourishment  from  little  green  Myxophy- 
FiG.  95.— Section  ceac  oY  ChlorophycesB  to  which  the  fila- 
ments attach  themselves  parasitically. 
These  little  hosts,  which  at  first  live  free  in  water  or  on 
moist  surfaces,  eventually  come  to  live  in  the  midst 
of  the  moist  tissues  of  the  fungus  parasite.  They 
were  formerly  supposed  to  be  parts  of  the  lichen  itself, 
and  were  called  "gonidia,"  an  objectionable  term  which 
is  still  in  common  use. 

340.  Disk  Lichens  are  all  of  rather  small  size,  vary- 
ing from  a  millimeter  or  so,  to  20  or  30  centimeters  in 
length.  For  the  greater  part  the  plant-body  is  flattish, 
and  adherent  to  the  surface  upon  which  it  grows,  but 


DISK  LICHENS  215 

some  species  have  more  or  less  elongated  branching 
stems. 

341.  Lichens  propagate  by  the  escape  of  some  of  the 
algal  cells,  with  attached  fungal  filaments  by  means  of 
eruptive  areas  C'soredia")  on  the  plant  body.  When 
one  of  these  comes  to  rest  upon  a  favorable  substratum 
it  grows  directly  into  a  lichen  plant  body  like  the  original. 
Asexual  spores  appear  to  be  wanting. 

342.  The  sexual  organs  as  far  as  known  remind  one 
of  those  of  the  Red  Algae.  The  oogone,  which  is  a  spiral 
coil  of  cells,  sends  up  a  slender  trichogyne  to  the  surface 
of  the  plant  body.  Fertilization  takes  place  by  means  of 
minute  non-ciliated  sperms  which  are 
produced  in  countless  numbers  in  nearby 
cavities  (spermogones)  in  the  plant  body. 
The  sperms  come  in  contact  with  the  f^j 
projecting  trichogyne  (doubtless  aided 
by  water)  and  fertilize  the  oogone,  the  organs^ orcou^ml. 
result   of   which   is   the   rapid   upward 

growth  of  filaments,  the  enlarged  terminal  cells  of  which 
become  asci.  INIingled  with  the  asci  are  long  sterile  cells 
(paraphyses)  for  the  protection  of  the  asci  and  ascospores 
in  the  hymenial  layer,  which  forms  a  more  or  less  disk- 
shaped,  or  cup-shaped  fruit.  Such  open  fruits  are  known 
as  "apothecia, "  in  contrast  with  the  closed  fruits  C'peri- 
thecia")  of  many  of  the  fungi  to  be  taken  up  later. 

343.  The  ascospores  germinate  by  sending  out  one  or 
more  tubes  which  develop  directly  into  the  ordinary  fila- 
ments of  the  lichen-body.  Experiments  have  shown  that 
these  filaments  will  not  grow  for  any  great  length  of  time 
unless  they  come  into  contact  with  green  algae  of  the 
proper  species,  to  which  they  become  attached,  growing 
rapidly  and  surrounding  them.  On  the  other  hand,  in 
the  moist  tissues  thus  formed  the  green  algae  find  protec- 


216  PHYLUM  VII.     CARPOMYCETEAE 

tion  and  ample  opportunity  for  growing.  There  is  thus 
an  association  between  these  plants  which  is  mutually 
beneficial  (symbiosis);  the  fungus  lives  parasitically  upon 

the  green  algae,  to  which  in  return  it  furnishes 

shelter  and  moisture. 

344.  Among  the  Disk  Lichens  one  of  the 

simplest  is  the  Thread  Lichen  (Ephebe)  found 

on  wet  rocks.  In  it  the  fungus  filaments 
Fig.  97.  grow  ovcr  and  around  the  cells  of  Scytonema 
(parasitic^on  or  Stigoucma  filaments, 
cy  onema  .  ^^^^  Some  other  Disk  Lichens  are  parasitic 
upon  Nostoc  colonies,  as  in  the  Jelly  Lichens  (Collema, 
Leptogium),  while  for  the  greater  part  they  are  parasitic 
on  species  of  Protococcus,  as  is  the  case  with  the  great 
majority  of  common  lichens — Cladonia,  Theloschistes, 
Physcia,  Parmelia,  Ramalina,  Usnea,  etc. 

The  Cup-fungi  (ORDER  PEZIZALES) 

346.  The  common  Cup-fungus  of  the  woods  is  a  typical 
representative  of  this  order.  The  familiar  cup-  or  saucer- 
shaped  growth  is  in  reality  the  spore-fruit  C'apothecium"), 
while  the  plant  itself  is  out  of  sight.  The  plant  consists 
of  whitish,  septate  filaments  which  grow  on  or  in  the 
ground  or  in  rotten  wood,  drawing  their  nourishment  from 
decaying  vegetable  matter.  These  plants  are  therefore 
saprophytes.  Some  Cup-fungi,  however,  are  known 
to  be  parasites. 

347.  But  little  is  known  as  to  the  asexual  reproduction 
of  the  Cup-fungi,  but  in  some  species  conidia  have  been 
observed. 

348.  Thesexualorgansof  Pyronema("Peziza")are  pro- 
duced by  the  sweUing  up  of  the  ends  of  certain  of  the  fila- 
ments of  the  plant  into  globular  or  ovoid  cells,  the  oogones, 
each  having  a  projection  (trichogyne).     From  below  each 


CUP  FUNGI 


217 


oogone  a  slender  branch  grows  out,  and  becomes  the 
antherid,  which  soon  comes  into  contact  with  the  tricho- 
gyne.  FertiUzation  is  effected  by  the  passage  of  the 
nuclei  from  the  antherid  into  the  trichogyne  and  from 
thence  into  the  oogone.  As  a  result  numerous  branches 
start  out  from  the  oogone, 
forming  the  ascogenous 
hyphae.  At  the  same  time 
their  arise  numerous  sterile 
hyphae,  from  the  tissues 
beneath    the    oogone,    and 

,  ,  1      •     ,  Fig.  98. — Pcziza,  and  Pyronema. 

these    grow    upward    mter- 

mingling  with  the  ascogenous  hyphae,  forming  a  dense 
felted  mass,  which  gradually  takes  on  the  size  and  form 
of  the  spore  fruit.  The  upper  ends  of  the  ascogenous 
hyphae  become  enlarged  into  asci  in  which  spores 
are  developed,  while  the  sterile  hyphae  make  up  the 
remainder  of  the  apothecium,  some  of  them  standing 
among  the  asci  as  the  so-called  paraphyses.  The  asci 
and  paraphyses  all  reach  the  same  height,  and  make  up 
the  inner  surface  of  the  cup  (the  ''hymenium").  Upon 
escaping  from  the  asci,  the  spores  germinate  and  produce 
the  filamentous  plants. 


The  Morels  (ORDER  HELVELLALES) 

349.  Morels  are  related  to  the  Cup- 
fungi,  and  like  them  are  filamentous  sapro- 
phytes living  in  the  ground.  The  conical 
fruit  is  stalked,  and  its  upper  surface  is 
studded  with  hymenial  areas  in  which  are 
asci  and  paraphyses  similar  to  those  of 
the  preceding  order.  A  common  species 
is   Morchella   esculenia,    in    which    the   whitish  fruit  is 


218 


PHYLU.M  VII.     CARPOMYCETEAE 


poc 


Fig.  100. 
Exoascus. 


from  7  to  12  centimeters  high.     It  is  edible  and  bears 
the  name  of  Mushroom  in  the  central  United  States. 

350.  The  Plum-pocket  fungus  (Exoascus),  which  dis- 
torts the  young  plums  in  spring  and  early 
summer,  is  a  greatlj^  reduced  parasitic  sac 
fungus  (Order  Exoascales).  Here  the  plant 
consists  of  delicate  threads  which  penetrate 
the  tissues  of  the  plum,  eventually  producing 
on  the  surface  poorly  developed  asci  which  are 
not  aggregated  into  cups. 

351.  Two  additional  orders  of  Hchens — the  Slit  Lichens 
(Graphidalcs)  and  Closed  Lichens  (Pyrenolichenes)  are 
abundantly  represented  by  species  of  Arthonia,  Graphis, 
and  Endocarpon.  In  the  first  order  the  apothecia  are  so 
nearly  closed  as  to  leave  only  a  narrow  slit,  and  in  the 
second  the  asci  are  w^holly  enclosed,  the  fruits  being  peri- 
thecia,  with  only  a  minute  pore  or  none  at  all. 

352.  The  Slit-fungi  (Order  Hysteriales),  are  to  be 
associated  with  the  Slit  Lichens,  and  may  be  illustrated 
by  the  Black  Slit-fungus  (Hystero- 
graphium)  whose  saprophj^tic  fila- 
ments ramify  through  bark  or  old 
wood  and  eventually  produce  small, 
black,  narrow,  elongated,  sessile 
apothecia,  whose  edges  approximate, 
leaving  only  a  narrow  slit.  Each 
ascus  contains  eight  muriform, 
elongated  spores,  and  the  asci  are  intermixed  with 
branched  paraphyses. 


Fig.    101. — Ilysterogra- 
phium. 


The  Closed  Fungi  (ORDER  PYRENOMYCETALES) 

353.  The  plants  of  this  order  are  parasitic  or  saprophy- 
tic filaments,  and  their  spore-fruits,  which  are  simple  or 
compound,  are  usually  hard  and  somewhat  coriaceous. 


BLACK  KNOT  219 

354.  A  good  illustration  of  the  plants  of  this  order  is 
the  Black  Knot  {Plowrighiia  morbosa),  which  attacks  the 
plum  and  eherr}^  In  the  spring  the  parasitic  filaments, 
which  the  previous  year  penetrated  the  3'oung  bark, 
multiply  greatly,  and  finally  ])reak  through  the  ])ark, 
and  form  a  dense  tissue.  The  knot-like  mass  grows 
rapidly,  and  when  full-sized  is  usually  from  2  or  3  to  10  or 
15  centimeters  long,  and  from  1  to  3  centimeters  in 
thickness;  it  is  solid  and  but  slightl}^  yielding,  and  is 
composed  of  filaments  intermingled  with  an  abnormal 
development  of  the  bark-tissues  of  the  host-plant. 

355.  The  knot  at  this  time  is  dark-colored,  and  has  a 
velvety  appearance,  which  is  due  to  the 
fact  that  its  surface  is  covered  with 
myriads  of  short,  jointed,  vertical  fila- 
ments, each  of  which  bears  one  or  more 
conidia.  The  conidia,  which  fall  off 
readily,  are  produced  until  the  latter  part 
of  summer,  when  the  filaments  which 
bear  them  shrivel  up  and  disappear. 

356.  During  the  autumn  asci  are  produced,  but  re- 
quire the  greater  part  of  winter  to  come  to  perfection. 
The  asci  grow  in  the  cavities  of  minute  papillae  {peri- 
thecia),  and  are  intermingled  with  slender  filaments 
(paraphj'ses).  Each  ascus  contains  eight  spores,  which 
eventually  escai)e  through  an  ai)ical  pore.  These  spores 
germinate  by  sending  out  a  small  filament,  or  sometimes 
two. 

357.  No  sexual  organs  have  as  yet  been  observed. 
Possibly  they  exist  in  the  dense  tissues  of  the  knot,  and 
fertilization  may  occur  in  the  spring  or  early  summer, 
but  they  may  have  disappeared  through  the  excessive 
parasitism  of  these  plants. 

358.  The  parasitic  filaments  of  each  year's  knot  gener- 


220  PHYLUM  VII.     CARPOMYCETEAE 

ally  penetrate  downward  some  centimeters  into  the  unin- 
jured bark,  and  remain  dormant  there  until  the  following 
spring,  when  they  begin  the  growth  which  results  in  the 
production  of  a  new  knot,  as  described  above. 

359.  To  this  order  belongs  the  Ergot  (Claviceps),  a 
common  parasite  upon  heads  of  rye,  and  also  many  of 
the  black  growths  upon  the  bark  and  wood  of  trees. 
Many  species  produce  black  spots  upon  living  leaves, 
wdiile  many  others  occur  upon  dead  leaves  and  twigs. 

360.  The  Closed  Fungi  include  a  large  number  of 
exceedingly  injurious  species;  they  often  attack  and 
destroy  not  only  plants,  but  also  insects,  upon  which 
their  ravages  are  sometimes  very  great. 

The  Mildews  (ORDER  PERI SPORI ALES) 

361.  These  plants,  which  are  mainly  parasitic,  are 
composed  of  branching  septate  filaments  (hyphae)  which 
form  a  white  or  dark  web-like  film  upon  the  surface  of  the 
leaves  and  stems  of  their  hosts.  There  are  both  sexual 
and  asexual  spores,  and  of  the  latter  there  are  in  some 
cases  two  or  three  different  kinds,  which  are  produced 
earher  than  those  that  result  from  a  fertilization. 

362.  In  the  Powdery  Mildews  (Family  Erysiphaceae)  ^ 
which   are   all   parasitic,   the  jointed   filaments   closely 

cover  the  leaves  and  other  tender  parts 
of  many  plants,  and  draw  nourishment 
from  them  by  means  of  suckers  (hausto- 
ria),  w^hich  project  as  irregular  out- 
growths from  the  side  next  to  the  epi- 

^'"'o/Er^Tiphe'^'^  dermis.  These  suckers  apply  them- 
selves closely  to  the  epidermal  cells,  and 

penetrate  them. 

363.  The  crossing  and  branching  filaments  soon  send 
up  many  vertical  branches,  which  continue  to  form  new 


POWDERY  MILDEWS  221 

cells  below  by  cross  partitions.  The  cells  thus  formed  are 
at  first  oblong  and  cyhndrical,  with  flattened  ends;  but 
the  topmost  ones  soon  become  rounded  at  their  extremi- 
ties, thus  giving  rise  to  a  row  of  cells,  the  spores,  or 
conidia.  These  fall  off  successively  and  germinate  at  once 
by  pushing  out  a  tube,  which  gives  rise  to  a  new  plant. 

364.  The  sexual  process  (generation)  in  most  species 
takes  place  late  in  the  season.  Two 
filaments  crossing  each  other  or  coming 
into  close  contact  swell  slightly  and  send 
out  from  each  a  short  branch;  one  of 
these  becomes  the  oogone,  and  the  other 
the   antherid,   both   organs  being  very    fig  104— Gcncm- 

much  reduced.  tion  of  Erysiphaceae. 

365.  Fertilization  is  effected  by  the  direct  union  of 
protoplasm.  Eight  or  ten  branches  then  bud  out  below 
the  oogone,  and  growing  upward  soon  completely  enclose 
it  in  a  cellular  coat  which  eventually  becomes  hardened 
and  turns  brownish  in  color,  constituting  the  spore-fruit 
(perithecium). 

366.  The  oogone  inside  of  the  perithecium  gives  rise, 
by  branching,  to  one  or  more  large  cells  (young  asci) 
filled  at  first  with  granular  protoplasm,  which  soon  forms 
two  to  eight  spores  (ascospores) ,  Upon  its  outer  surface 
the  spore-fruit  develops  long  filaments  (known  as 
** appendages''),  probably  for  holdfasts.  In  some  genera 
these  terminate  in  hooks;  in  others  they  are  dichotom- 
ously  branched;  in  still  others,  needle-shaped;  while  in 
many  species  they  end  irregularly.  The  spore-fruits  re- 
main during  the  winter  upon  the  fallen  and  decaying 
leaves,  and  finally,  by  rupturing,  permit  the  asci,  with 
the  contained  spores,  to  escape. 

367.  The  Herbarium-mold  (Aspergillus)  is  related  to 
the  Mildews  and  belongs  to  the  order  of  Little  Tubers 


222  PHYLUM  VII.     CARPOMYCETEAE 

(AspERGiLLALEs).  It  is  commoii  on  poorly  dried  speci- 
mens in  the  herbarium,  and  also  on  moldy  hay  and  decay- 
ing vegetation  generally.  It  sends  up  vertical  branches, 
which  swell  at  the  top  and  bear  a  great  number  of  small 
protuberances  (the  sterigmata) ,  each  of  which  produces 
a  chain  of  conidia. 

368.  The  sexual  organs  appear  a  little  later  than  the 
conidia.     The  end  of  a  branch  of  the  plant  becomes 

coiled  into  a  hollow  spiral  which  con- 
stitutes the  oogone.  From  below  the 
spiral  an  antherid  grows  upward,  and 
brings  its  apex  into  contact  with  the 
upper  cells  of  the  oogone.  After  fer- 
tilization other  branches  grow  up 
Fig.  105.— Aspergillus,  arouud  the  oogouc,  and  finally  com- 
pletely enclose  it,  as  in  the  Mildews, 
described  above.  In  the  meantime  from  the  cells  of  the 
enclosed  oogone  branches  bud  out,  and  finally  produce 
many  eight-spored  asci  on  their  extremities;  later  the 
asci  are  dissolved,  and  the  spore  fruit,  now  of  a  sulphur- 
yellow  color,  contains  a  multitude  of  loose  spores. 

369.  The  Blue  Molds  (species  of  Penicillium)  are 
related  to  Aspergillus.  The  conidial  stage  is  a  common 
Blue  Mold  on  decaying  fruit  and  pastry.  The  sexual 
organs  resemble  those  of  the  herbarium-mold,  and  the 
spore-fruit  is  a  minute  truffle-like  body  as  large  as  a 
coarse  sand-grain. 

370.  Yeast-plants.  A  still  greater  degradation  of  the 
sac-fungus  type  is  reached  in  the  minute  plants  which 
occur  in  yeast.  If  a  bit  of  yeast  be  placed  upon  a  glass 
slip  and  carefully  examined  under  high  powers  of  the 
microscope,  there  will  he  seen  very  many  small  roundish 
or  oval  cells,  of  a  pale  or  whitish  color.  They  have  a 
cell-wall,  but  generally  the  nucleus  is  indistinct.     These 


YEAST  PLANTS  223 

little    cells   are    Yeast-plants,    and    bear    the   name    of 
Saccharomyces  cerevisiae. 

371.  The}'  reproduce  l^y  a  kind  of  fission,  called 
"budding.''  Eacli  cell  ]nishes  out  a  little  projection 
which  grows  larger  and  larger,  and  finally  a  cell-wall 
forms  between  it  and  the  old  cell  and  these  sooncT  or 
later  separate  from  one  another.  Under 
favorable  circumstances  certain  cells  form 
spores  internally,  and  these  are  now  re- 
garded as  asci,  homologous  with  the  asci 
of  the  higher  sac-fungi.  Yeast-plants  are, 
therefore,  to  be  considered  as  greatly  sim-  Fig.  iog.— Sac- 
plified  Sac-fungi,  and  they  are  members  of  ^  ^romyces. 
the  family  Saccharomycetaceae  (of  the  Order  Hemi asc ales) 
which  has  experienced  what  is  probably  the  greatest 
reduction  suffered  by  any  plants  of  the  Ascosporeae, 

372.  Yeast-plants  are  saprophytes,  and  live  upon  the 
starch  of  flour.  They  break  up  the  starch,  and  in  the 
process  liberate  considerable  quantities  of  carbon  dioxide 
which  appears  as  bubbles  upon  the  surface  of  the  j^east. 
Another  result  of  the  l^reaking  up  of  the  starch  is  the 
formation  of  alcohol;  hence  the  growth  of  yeast-plants  in 
a  starchy  substance  is  always  accompanied  by  what  is 
known  as  alcoholic  fermentation.  The  housewife  and 
baker  use  yeast-plants  for  the  carbon  dioxide  gas  which 
they  evolve,  to  give  lightness  to  the  bread,  while  the 
brewer  and  distiller  use  the  same  plants  for  the  alcohol 
produced  b}'  their  activity.  (See  Chapter  IV,  paragraph 
139.) 

373.  The  Truffles  (Order  Tuberales)  are  well  known 
from  their  large  underground  spore-fruits,  which  are 
edible.  Internally  there  are  narrow  tortuous  channels 
on  whose  walls  asci  develop,  each  containing  a  numl)er  of 
spores.     Little  is  known  of  their  round  of  life,  and  the 


224  PHYLUM  VII.     CARPOMYCETEAE 

sexual  organs  have  not  been  discovered.  The  part  of 
the  truffle  that  we  eat  is  the  large  spore-fruit.  These 
are  collected  in  Europe  by  experts  and  preserved  for  the 
market,  where  they  command  high  prices. 

Laboratory  Studies,  (a)  Collect  fruiting  specimens  of  the 
common  fruticosc  lit-hcn  (Usnca),  which  grows  upon  branches 
of  trees  in  forests.  Make  thin  cross-sections  of  the  stem,  mount 
in  alcohol,  afterward  adding  dilute  potassium  hydrate.  Study 
the  filaments  and  their  relation  to  the  algae.  Isolate  some  of 
the  algae  by  tapping  on  the  cover-glass,  and  note  their  resem- 
blance to  Green  Shme  (Protococcus). 

(6)  Make  thin  vertical  sections  through  one  of  the  fruiting 
disks,  mount  as  above,  and  study  asci,  ascospores  and  para- 
physes. 

(c)  Collect  some  of  the  small,  flat,  many-lobed  hchens  which 
grow  on  the  bark  of  apple-,  maple-,  and  oak-trees,  and  which 
have  small  blackish  fruit-disks.  Make  careful  sections  of  the 
plant-body  through  the  fruit-disks,  and  study  the  whole  struc- 
ture, ascospores,  asci,  paraphyses,  filaments,  and  algae. 

(d)  Search  for  cup-shaped  fungi,  in  the  spring,  about  old 
hot-beds  and  upon  well-rotted  barnyard-refuse.  A  common 
cup  fungus  of  an  amber  color  often  to  be  met  with  in  such 
localities  is  one  of  the  best  for  the  study  of  ascospores  and  asci. 
Make  very  thin  sections  at  right  angles  to  the  inner  surface. 

(e)  Collect  the  bright  red  saucer-shaped  cup-fungus  {Sar- 
coscypha  coccinea)  growing  in  the  woods  upon  decaying  sticks 
and  having  a  diameter  of  1  to  4  centimeters.  Make  similar 
sections. 

(/)  Collect  a  few  Morels  {Morchella  esculenta),  and  make 
sections  at  right  angles  to  the  surface  of  the  pits  which  cover 
the  upper  portion  and  examine  for  ascospores  and  asci. 

(g)  Collect  fresh  specimens  of  Plum  Pockets,  and  preserve 
them  in  alcohol.  Study  the  fungus  by  making  very  thin 
sections  at  right  angles  to  the  surface.  Each  ascus  will  be 
found  to  contain  several  rounded  ascospores. 

(h)  Collect  Sht-fungi  (Hystcrographium)  on  the  bark  of  oak 
or  ash  trees,  or  on  dead  twigs  of  sumach,  and  other  shrubs. 
The  apothecia  are  black  and  carbonaceous,  and  are  about  a 
millimeter  long. 


LABORATORY  STUDIES  225 

(i)  In  early  summer  examine  the  choke-cherry  and  plum 
trees  (wild  and  cultivated)  for  the  3'oung  stages  of  Black  Knot. 
Watch  the  development  until  the  knot  becomes  velvety  in 
appearance  (about  midsummer).  Now  make  very  thin  cross- 
sections  of  the  knot  and  examine  for  conidia.  The  several 
stages  may  be  readily  preserved  in  alcohol  for  future  study. 

(j)  Late  in  autumn  and  in  early  winter  examine  the  knots  on 
the  same  trees.  Note  the  young  perithecia,  i.e.  hollow  paj)illae. 
Make  very  thin  vertical  sections  through  some  of  these.  No 
perfect  ascospores  can  be  found  at  this  time. 

(k)  Collect  fresh  knots  in  midwinter  and  make  similar 
examinations,  when  the  asci  and  ascospores  may  be  found. 

(/)  In  the  autumn  collect  a  quantity  of  leaves  of  the  lilac 
which  are  covered  with  a  whitish  mold-like  growth,  the  Lilac- 
mildew  (Microsphaera  alni).  Scrape  off  a  bit  of  this  Mildew 
after  moistening  with  a  drop  of  alcohol;  mount  carefully, 
adding  a  httle  potassium  hydrate.  Look  for  conidia  and 
haustoria.  Look  also  for  spore-fruits,  which  appear  like  minute 
dark  dots  to  the  naked  eye.  Carefully  crush  the  spore-fruits 
and  observe  the  asci  (four  to  seven)  with  their  contained 
ascospores  (6).  Note  the  beautifully  branched  tips  of  the 
appendages. 

(m)  Collect  and  study  the  mildews  to  be  found  on  hops 
(Sphaerotheca  castagnei),  on  cherry-  and  apple-leaves  {Podo- 
sphaera  oxyacanthae) ,  on  hazel-  and  ironwood-leaves  (Phyl- 
lactinia  suffulta),  on  willow-leaves  {Uncinula  salicis),  on  leaves 
and  fruit  of  grapes  {U.  necator),  on  wild  sunflowers,  verbenas, 
etc.  (Erysiphe  cichoraccanun) ,  on  peas,  grass,  anemones, 
buttercups,  etc.  {E.  comynunis). 

(n)  Place  a  few  shps  of  green  twigs  in  an  ordinary  plant-press, 
allowing  them  to  remain  until  they  become  (1)  moldy  (conidial 
state),  and  (2)  covered  with  minute  yellow  globular  bodies  (the 
spore-fruits) .  These  are  known  as  the  Herbarium-mold  (.1  spcr- 
gillus  herhariorum) .  Study  as  in  the  case  of  the  Mildews. 
This  can  frequently  be  obtained  by  placing  a  piece  of  almost 
dry  bread  under  a  bell  jar  for  a  few  days. 

(o)  Blue  Mold  may  be  obtained  from  decaying  fruit,  pas- 
try, etc. 

(p)  Place  a  minute  piece  of  "compressed"  yeast  upon  a  glass 
sHde,  add  a  little  water,  cover  with  a  cover-glass,  tapping  it 
down  gently.     After  a  short  examination  under  a  high  power  of 

15 


226  PHYLUM  VII.     CARPOMYCETEAE 

the  microscope  add  iodine,  which  will  stain  the  starch-grains 
blue  or  purple,  and  the  yeast-plants  j^ellowish.  Alany  of  the 
latter  will  be  found  in  process  of  budding. 

(q)  Repeat  experiment  q  on  page  103  for  production  of 
carbon  dioxide  by  yeast. 

(?')  Spread  a  little  ''compressed"  yeast  on  a  fresh-cut  shce 
of  potato  or  carrot;  cover  with  a  tumbler  or  l^ell-jar  to  kee]:)  it 
moist;  after  a  few  daj^s  (four  to  eight)  examine  for  cells  which 
are  producing  ascospores. 

(s)  Commercial  Truffles  are  natives  of  Europe,  but  they  may 
be  obtained  for  study  in  our  markets.  Make  thin  cross- 
sections  of  the  large  spore-fruit  and  examine  the  ascospores  and 
asci. 


Class  15.     BASIDIO  SPORE  AE 

The  Basidium  Fungi 

374,  The  plants,  or  rather  the  fruits,  of  this  class  are 
among  the  largest  and  most  conspicuous  of  the  fungi. 
They  are  mostly  saprophytes  whose  abundant  vegetative 
filaments  {viycelium)  ramify  through  the  nourishing  sub- 
stance, and  afterw^ard  give  rise  to  the  conspicuous  spore 
fruits.  The  spores  are  produced  usually  in  4's  upon 
slender  outgrowths  from  the  ends  of  enlarged  cells  {ha- 
sidia),  the  latter  usually  arranged  parallel  to  each  other 
so  as  to  form  a  spore-bearing  surface  Qiymenium) ,  which 
may  be  external  (as  in  Toadstools)  or 
internal  (as  in  Puff-balls). 

375.  The  basidia  in  this  class  are 
here  regarded  as  homologous  wdth  the 
asci  of  the  Ascosporeae.  The  differ- 
ence between  them  is  that  in  the  asci 
mento?''bI^Sia''a°nd  the  sporcs  iu  their  development  remain 
basidiospores.  inside  of  the  ascus  cavity,  while  in  the 

basidia  the  spores  as  they  develop  push  out  so  as  finally 
to  become  external.     It  is  obvious  that  the  ascus  is  the 


PUFF  BALLS  227 

more  primitive  structure,  and   that  the  basidium   is  a 
hiter  and  a  higher  structure,  probabl}^  derived  from  it. 

376.  There  are  about  14,000  species,  which  may  be 
separated  into  nine  orders,  and  about  twenty-five  fami- 
lies.    A  few  only  of  these  will  be  taken  up  here. 

377.  The  lowest  of  the  Basidium-fungi,  the  False 
Tubers  (Order  Hymenogastrales)  are  subterranean 
plants,  with  subterranean  truffle-like,  fleshy  fruits,  which 
like  the  truffles  are  edible  and  wholesome.  They  are 
distinguished  from  the  truffles  by  the  fact  that  they  con- 
tain basidia  instead  of  asci. 

378.  The  Pufif-balls  (Order  Lycoperdales).  The 
plants  of  this  order  are  saprophj^tes,  whose  spore  fruits 
are  often  of  large  size,  and  usually  more  or  less  globular  in 
form.  The  basidiospores  are  always  borne  in  the  in- 
terior of  more  or  less  regular  cavities,  and  from  these  they 
escape  by  the  deliquescence,  and  subsequent  drying  and 
rupture  of  the  surrounding  tissues. 

379.  The  vegetative  filaments  of  Puff-balls  penetrate 
the  substance  of  decaying  wood,  and  the  soil  filled  with 
decaying   organic   matter.      They 
usually  aggregate  themselves  into 
cylindrical  root-like  masses.     After 
an  extended  vegetative  period  the 
filaments  produce  upon  their  root-     fig.  los.— Puff-haii  and 
like  portions  small  rounded  bodies,  basidiospores. 

the  young  spore  fruits,  which  increase  rapidly  in  size  and 
assume  the  forms  characteristic  of  the  different  genera. 

380.  No  sexual  organs  have  yet  been  discovered,  but 
analogy  points  to  their  possible  existence  upon  the  vege- 
tative filaments  just  previous  to  the  first  appearance  of 
the  spore  fruits.  The  spore  fruits  are  composed  of  inter- 
laced filaments  loosely  arranged  in  the  interior,  and  an 
external  more  compact  limitary  tissue  forming  a  rind 


228  PHYLUM  VII.     CARPOMYCETEAE 

(peridium) .     The  basidia  develop  in  a  portion  of  the  in- 
terior (the  gleba),  the  remainder  being  sterile. 

381.  Many  common  puff-balls  belong  to  the  genus 
Lycoperdon,  the  type  of  the  family  Ly coper daceae,  of 
which  there  are  a  good  many  species.  The  genus  Cal- 
vatia  contains  the  Giant  Puff-ball  (C.  maxima),  whose 
spore  fruit  is  sometimes  30  centimeters  or  more  in  diam- 
eter. Here  it  must  be  remembered  that  the  proper  plant 
lives  underground,  obtaining  its  food  from  decaying  vege- 
table matter,  while  the  great  ball  is  a  fruit  containing 
basidia  and  basidiospores. 

382.  The  Bird-nest  fungi  (Order  Nidulariales)  are 
so  noticeable  that  they  should  be  examined  here.  These 
little  fruits  usually  grow  on  twigs  and  sticks,  and  are 
closed  at  first,  and  then  open  and  cup  shaped.  They  are 
a  centimeter  or  less  in  height  and  width,  and  when  mature 
contain  several  small  brownish  spore  packets  (the  ''eggs'' 
of  the  little  *' nests").  When  young  these  *'eggs"  are 
small  cavities  lined  with  basidia  and  surrounded  by  a 
dense  layer  of  hyphae.  When  the  tissues  about  them 
deliquesce  these  spore-bearing  cavities  persist  as  hard 
walled  bodies. 


\A 


Fig.   109. — Development  Fig.  110. — Development 

of  bird-nest  fungi.  of  stinkhorn. 

383.  The  Stink -horns  (Order  Phallales)  live  as  sap- 
rophytes, feeding  upon  decaying  organic  matter  in  the 
ground,  or  less  frequently  as  parasites  in  the  roots  of 
various  plants,  eventually  developing  globose  subterra- 
nean fruits.     These  fruits  produce  their  spores  in  a  circu- 


TOADSTOOLS  229 

lar  layer,  and  when  mature  become  ruptured  by  the  rapid 
growth  of  their  central  tissues,  resulting  in  the  formation 
of  a  stalk  which  carries  up  the  slimy  mass  of  spores  to 
some  distance  above  the  ground.  The  intolerable  odor 
of  most  of  the  species  has  earned  for  them  their  inelegant 
but  quite  appropriate  common  name. 

384.  The  Toadstools  (Order  Agaricales).  The  fruits 
of  these  plants  in  some  respects  are  the  highest  of  the 
Carpomj'ceteae.  They  are  not  only  of  considerable  size 
(ranging  from  1  to  20  centimeters,  or  more,  in  height), 
but  their  structural  complexity  is  so  much  greater  than 
that  of  the  other  orders  that  they  must  be  regarded  as  the 
highest  of  the  fungi.  Like  the  Puff-balls,  they  produce 
an  abundance  of  vegetative  filaments  (mycelium)  under- 
ground or  in  the  substance  of  decaying  wood.  These 
filaments  are  loosely  interwoven,  becoming  in  some  cases 
densely  felted  into  tough  masses  or  compacted  into  root- 
like forms.  While  mostly  saprophytic  some  appear  to  be 
parasitic,  especially  on  the  woody  tissue  of  trees  which  are 
rotted  by  them.  Sooner  or  later  these  underground 
filaments  produce  the  spore  fruits,  which  are  mostly 
umbrella-shaped,  as  in  common  Toadstools  and  Mush- 
rooms, or  of  various  more  or  less  irregular  shapes,  as  in 
the  Pore  fungi,  Coral  fungi,  etc. 

385.  The  Mushrooms  of  the  markets  (Agaricus  cam- 
pcstris)  so  connnonly  cultivated  by  gardeners,  may  illus- 
trate the  mode  of  development  of  the  Toadstools  (Family 
Agaricaceac).  The  vegetative  filaments  compose  the  so- 
called  ''spawn"  which  grows  through  the  decaying  matter 
from  which  it  derives  its  nourishment.  Upon  this  at 
length  little  rounded  masses  of  filaments  arise,  which  be- 
come larger  and  larger  and  are  the  young  fruits.  The 
circular  spore-bearing  layer  is  first  internal  and  su])ter- 
ranean  as  in  the  Stink-horns,  but  it  is  brought  above 


230  PHYLU.M  VII.     CARPO^IYCETEAE 

ground  by  tlie  rapid  growth  of  a  central  mass  of  stalk 
tissue,  and  later  by  a  rupture  of  tissues  the  hymenium  be- 
comes external. 

386.  At  maturity  the  spore  fruit  of  the  Mushroom 
consists  of  a  short  thick  stalk,  bearing  an  expanded  um- 
brella-shaped cap,  beneath  which 
are  many  thin  radiating  plates,  the 
gills.  Each  gill  is  a  mass  of  fila- 
ments whose  enlarged  end-cells 
(basidia)  come  to,  and  completely 

Fig.  111. -Development  of     covcr,  both  of  its  surfaccs.      The 

mushroom.  basidla  produce  spores  in  the  usual 

manner  for  plants  of  this  class,  that  is,  upon  slender  stalks. 

387.  In  the  Pore  fungi  (Polyporaceae)  the  basidia  line 
the  sides  of  pores;  in  the  Prickly  Fungi  (Hydnaceae)  and 
Coral  fungi  (Clavariaceae)  they  cover  the  surface  of  spines 
and  branches;  while  in  the  Leathery  fungi  (Thelephora- 
ceae,  Stereum,  etc.)  they  form  a  smooth  surface. 

388.  Nothing  is  yet  known  as  to  their  sexual  organs. 
Several  botanists  have  described  such  supposed  organs 
upon  the  vegetative  filaments  before  the  formation  of  the 
spore  fruit,  but  there  are  grave  doubts  as  to  the  correct- 
ness of  the  observations,  and  it  is  the  general  opinion  that 
these  organs  have  become  obsolete. 

389.  The  vegetative  filaments  (mycelium)  of  some 
species  of  this  order  (as  Foines  fovientariiis,  etc.)  often 
form  thick,  tough,  whitish  masses  of  considerable  extent 
in  trees  and  logs. 

390.  We  know  but  little  as  to  the  germination  of  the 
spores  and  the  subsequent  development  of  the  vegetative 
filaments. 

391.  Several  families  of  more  or  less  reduced  basidium 
fungi  which  probably  have  been  derived  from  the  fore- 
going families,  as  the  Ear  Fungi  (Auriculariales) ,  Jelly 


i 


LAHOUATORV  STUDIES  2:U 

Fungi  (Tremellales)  and  the  ytill  more  reduced  Exoha- 
sidiales  are  probably  to  be  placed  here. 

Laboratory  Studies,  (a)  Collect  specimens  of  puff-balls  in 
various  stages  of  growth.  IMake  very  thin  sections  of  the  young 
spore  fruit,  and  look  for  the  cavities  lined  with  spore-bearing 
cells  (basidia). 

(b)  JMount  in  alcohol  some  of  the  dust  which  escapes  from  a 
dry  iniff-ball.  Examine  with  a  high  power,  and  note  the  spores 
and  fragments  of  brokcn-up  filaments. 

(c)  Dig  up  tiie  earth  under  a  cluster  of  young  i)ufT-balls,  and 
observe  the  vegetative  filaments.  Examine  some  of  these 
filaments  under  the  microscope. 

(d)  In  the  summer  look  for  Earth  Stars  (Geaster)  in  which 
the  outer  peridium  is  rolled  back  (open)  when  wet,  and  closed 
when  dry. 

(e)  Stalked  Puff-balls  (Tylostoma)  may  often  he  found  witli 
a  stallv  3  to  10  or  more  centimeters  long  holding  the  spore 
cavit}'  aloft. 

(/)  Look  for  Bird-nest  fungi  in  fruit  on  sticks  and  twigs  on 
damp  ground.  Note  that  when  j^oung  the  fruits  are  closed 
and  solid,  and  that  as  they  become  older  much  of  the  internal 
tissue  deliquesces,  leaving  the  little  egg-like  spore  packets. 

(g)  Collect  specimens  of  Stink-horns  in  various  stages  of 
development  and  preserve  in  formalin.  Make  vertical  sections 
of  the  immature  (globose)  spore  fruit  and  note  the  circular 
spore  layer.  Study  the  basidia  and  basidiospores  under  a 
high  power. 

(h)  Collect  a  few  toadstools  in  various  stages  of  development, 
securing  at  the  same  time  some  of  the  subterranean  vegetative 
filaments.  Note  the  appearance  of  the  young  spore  fruits, 
and  how  they  develop  into  the  mature  toadstool. 

(0  Select  a  mature  (but  not  old)  spore  fruit  with  dark- 
colored  spores,  cut  away  the  stem,  and  place  the  top  (pileus) 
on  a  sheet  of  white  paper,  with  the  gills  down.  In  a  few  hours 
many  spores  will  be  found  to  have  dropi)ed  from  the  gills  uj)on 
tlic  paper;  these  are  the  so-called  "spore-prints". 

(j)  Examine  the  minute  structure  of  various  parts  of  tiie 
spore  fruit  and  the  vegetative  fdaments,  and  ol)servo  that  tiiey 
are  composcnl  of  rows  of  cylindrical  colorless  oolis  joiiunl  end  to 
end. 


232  PHYLU:M  VII.     CARPOMYCETEAE 

(k)  Make  very  thin  cross-sections  of  several  of  the  gills  and 
carefully  mount  in  water  or  alcohol.  Note  the  layer  of  spore- 
bearing  cells  (hymenium),  with  basidiospores  borne  upon  little 
stalks. 

(/)  Examine  the  pores  of  fresh  polypores  in  transection, 
looking  for  the  basidia  and  basidiospores  in  the  pores. 

(w)  In  like  manner  make  transections  of  Prickly  Fungi, 
Coral  Fungi,  and  Leathery  Fungi,  but  in  these  look  for  basid- 
iospores on  the  outer  surface  of  the  sections. 

Class  16.    TELIOSPOREAE.     The  Brand-Fungi 

392.  Here  are  collected  a  considerable  number  (4200 
species)  of  extremely  parasitic  fungi,  certainly  related  to 
the  fungi  of  the  two  preceding  classes.  On  account  of 
their  excessive  parasitism  they  are  structurally  much  re- 
duced and  degraded  and  this  has  served  to  hide  their  true 
relationship. 

393.  The  plant  body  consists  of  branching  septate 
filaments  which  run  through  the  green  tissues  of  higher 
plants,  eventually  producing  usually  erumpent  spore 
clusters  (sori),  but  no  definite  spore  fruits  (perithecia,  or 
apothecia).  Conidia  of  one  or  two  kinds  are  usually 
present,  and  precede  the  formation  of  teliospores. 

394.  The  Rusts  (Order  Uredinales)  are  minute, 
parasitic,  greatly  degraded  fungi 
which  grow  in  the  tissues  of  higher 
plants. 

395.  A  common  Wheat  rust 
{Puccinia  graminis)  may  be  taken 
oraeciospores  and  pycnio-  as  au  illustratiou  of  the  ordcr.  It 
is  common  wherever  wheat  is 
grown,  and  often  greatly  injures  and  sometimes  entirely 
destroys  the  crop.  Its  round  of  life  shows  four  well- 
marked  stages,  as  follows:  (I)  In  the  spring  clusters  of 
minute    yellowish    cups    occur    on    the    leaves   of  the 


WHEAT  RUST  233 

BarbciT}'.  These  cups  are  at  first  internal  rounded 
bodies,  in  which  spores  (conidia)  develop  in  chains, 
at  length  bursting  through  the  lower  epidermis.  The 
spores  quickly  drop  out  and  are  carried  away  by  the 
winds.  This  stage  is  known  as  the  cluster-cup  stage, 
and  the  spores  as  aecidiospores,  or  aeciospores. 

396.  Associated  with  this  cluster-cup  stage  there  are 
usually  flask-shaped  structures  known  as  spermogones  or 
pycnia,  in  which  minute  spores  or  spore-like  bodies 
(pycniospores)  are  produced.  They  resemble  the  struc- 
tures which  produce  sperms  in  the  Disk  Lichens.  If 
they  have  a  similar  function  in  the  rusts  it  has  not  yet 
been  demonstrated. 

397.  (II)  The  aeciospores  falling  upon  a  wheat  plant 
germinate  there  and  penetrate  its  tissues,  through  the 
stomata,  sending  haustoria  into  the  cells.  After  a  few 
days,  if  the  weather  has  been  favorable,  the  parasite  has 
grown  sufficiently  to  begin  the  formation  of  large  red- 
dish spores  (uredospores,  or  urediniospores)  just  beneath 
the  epidermis,  which  is  soon  ruptured,  exposing  the 
spores  in  reddish  lines  or  spots  upon  the  stems  and  leaf 
sheaths.  This  is  the  Red-rust  stage,  so  common  before 
wheat-harvest.  These  red  spores  fall  easily,  and  quickly 
germinate  on  wheat  again,  producing 
more  Red  rust,  and  so  rapidly  increasing 
the  parasite. 

398.  (Ill)  Somewhat  later  in  the  season 
the  parasitic  filaments  which  have  been 
producing  Red-rust  spores  begin  to  pro-      fig.  113— uredo- 
duce     the     dark-colored,    thick-walled,     l^nd'sporidsi""^"'^' 
2-spored    bodies    characteristic    of    the 

Black  Rust.  Each  2-spored  body  consists  of  a  contin- 
uous wall  tightly  enclosing  the  two  spores,  here  called 
*'teliospores."     Being  thick-walled,  these  spores  endure 


234  PHYLUM  VII.     CARPOMYCETEAE 

the  winter  without  injury,  antl  when  spring  comes  (IV) 
they  germinate  on  the  rotting  straw  forming  a  4-celled 
**promyceHum"  and  producing  several  (usually  four) 
minute  spores,  called  sporids.  This  is  the  fourth  and 
last  stage  of  the  rust.  Such  sporids  as  fall  upon 
Barberry-leaves  germinate,  and  enter  directly  through 
the  epidermis,  giving  rise  to  cluster  cups  again. 

399.  These  stages  (I,  II,  III)  are  so  different  in  appear- 
ance that  for  a  long  time  they  were  regarded  as  distinct 
plants,  and  received  different  names.  Thus  the  first 
stage  was  classified  as  a  species  of  Aecidium,  the  second 
as  a  species  of  Uredo,  and  the  third  as  a  Puccinia.  We 
still  preserve  these  names  by  sometim.es  calling  the  spores 
of  the  first  aecidiospores  (or  aeciospores)  and  of  the  second 
uredospores  (or  urediniospores),  while  the  third  name  is 
retained  as  the  scientific  name  of  the  genus. 

400.  For  a  long  time  many  botanists  did  not  believe 
the  statement  that  this  Wheat  rust  lives  for  a  part  of  its 
life  upon  one  host  (barberry),  and  later  upon  another 
(wheat),  but  now  this  fact  (known  as  ''heteroecism")  is 
well  established  not  only  for  Wheat  rust,  but  also  for 
many  other  species. 

401.  The  sporids  cannot  ordiiiarily  produce  rust 
directly  upon  wheat,  probably  because  of  the  toughness 
of  the  epidermis;  but  it  has  been  claimed  (by  Plowright) 
that  when  sporids  germinate  upon  very  young  leaves  of 
wheat-seedlings  they  penetrate  the  epidermis  and  then 
soon  give  rise  to  a  red-rust  stage.  In  such  cases  the 
cluster-cup  stage  is  omitted.  Possibly  the  rusts  upon 
the  spring  wheat,  oats,  and  barley  in  the  Mississippi 
Valley  and  on  the  Great  Plains  where  barberry  is  rare 
are  sometimes  propagated  in  this  way.  It  has  been 
shown  also  that  on  the  Great  Plains  the  red  rust  lives 
through  the  winter  on  the  little  wheat  plants,  and  that 


SEXUALITY  OF  RUSTS  235 

its  spores  blow  to  the  north  in  the  spring  from  field  to 
field,  and  back  to  the  south  in  the  autumn.  Probably 
this  is  the  more  common  mode  of  propagation  upon  the 
Plains.  Recently  it  has  been  found  also  that  teliosporcs 
occur  on  and  in  wheat  kernels,  and  it  is  thought  that 
young  plants  may  be  infected  directly  from  these. 

402.  There  are  many  kinds  of  rusts,  distinguished 
mainly  by  their  teliospores,  which  are  single  (Uromyces 
and  Melampsora),  in  twos  (Puccinia  and  Gymnospor- 
angium),  or  several  (Phragmidium).  In  many  species 
the  round  of  life  is  similar  to  that  in  the  Wheat  rust 
described  above  (heteroecious),  the  hosts,  however,  being 
different,  but  in  others  there  appears  to  be  a  constant 
omission  of  certain  stages.  Moreover,  in  many  species 
all  the  stages  develop  upon  the  same  host  plant  (autoe- 
cious). 

403.  Cell  fusions  which  are  now  regarded  as  having 
a  sexual  significance,  and  whose  ultimate  result  is  the 
production  of  teUospores,  have  been  observed  in  the 
mycelium  of  some  of  the  rusts.  The  simple  sexual  or- 
gans (usually  end  cells  of  adjacent  filaments)  coalesce  into 
binucleate  cells,  which  develop  short  hyphae  of  cells  also 
binucleate.  In  some  cases  these  produce  directly  one 
or  more  teliospores;  in  others  one  or  two  additional  spore 
forms  are  intercalated  as  aeciospores  and  uredospores. 
Thus  we  may  have  either  aecia  or  uredinia  or  both  form- 
ing as  the  first  result  of  the  sexual  act,  but  in  any  event 
the  ultimate  result  is  the  production  of  teliospores. 
Accordingly  these  several  spore  forms  are  all  primarily 
binuclcated,  but  the  two  nuclei  unite  early  in  the  young 
teliospore,  and  therefore  the  promycelial  cells  and  sporids 
are  uninucleate. 

404.  The  Smuts  (Order  Ustilaginales).  The  i^lants 
which  compose  this  order  are  all  parasites  living  in  the 


236  PHYLU:^!  VII.     CARPOMYCETEAE 

tissues  of  Flowering  Plants.  Like  the  Rusts,  they  send 
their  parasitic  threads  through  the  tissues  of  their  hosts, 
and  afterward  produce  spores  in  great  abundance  which 
usually  burst  through  the  epidermis. 
There  is  a  still  greater  structural  degra- 
dation in  the  plants  of  the  present  order 
than  in  the  Rusts,  probably  due  to  their 
excessive  parasitism. 
Fig.    ii4.-TeUo-        405.    The    parasitic    threads    of    the 

spore  and  sponds.  *^ 

Smuts  are  well  defined,  and  consist  of 
thick-walled,  cellular,  branching  filaments,  which  are 
generally  of  very  irregular  shape.  They  grow  in  the 
intercellular  spaces  and  cell  cavities  of  their  hosts,  and 
some  send  out  suckers  {haustoria),  which  penetrate  the 
adjacent  cells  much  as  in  the  Mildews.  The  parasite 
generally  begins  its  growth  when  the  host  plant  is 
quite  young  (meristematic)  and  grows  with  it,  spreading 
into  its  branches  as  they  form,  until  it  reaches  the  place 
of  spore-formation.  In  perennial  plants  the  parasite 
may  be  perennial,  reappearing  year  after  year  upon  the 
same  stems,  or  upon  the  new  stems  grown  from  the  same 
roots;  in  annuals  it  must  obtain  a  foot-hold  in  the  young 
plants  as  they  grow  in  the  spring. 

406.  The  life  history  of  the  Smuts  has  been  made  out 
for  but  few  species.  Three  kinds  of  spores  (conidia, 
teliospores  and  sporids)  have  been  observed  in  many 
species,  and  their  germination  has  been  carefully  studied, 
but  the  sexual  organs  (if  any  exist)  have  not  yet  been 
discovered. 

407.  The  Smut  of  Indian  corn  (Ustilago  maydis)  is 
very  common  in  autumn.  The  parasitic  filaments  are 
found  in  various  parts  of  the  host,  and  at  last  those  which 
reach  the  young  kernels  or  other  succulent  parts  become 
semi-gelatinous  and  form   spores  internally.     There  is 


SMUTS  237 

much  crowding  and  distortion  of  these  soft-walled  spore- 
l)earing  fihunents,  but  here  and  there  this  structure  may 
be  made  out.  When  the  spores  are  ripe,  the  gelatinous 
walls  dissolve  and,  the  watery  portions  evaporating, 
leave  a  dust}'  mass  of  black  spores.  The  spores  germinate 
by  sending  out  a  short  septate  filament  (promycelium) 
upon  which  minute  sporids  are  formed  laterally,  much 
as  in  the  Wheat  rust.  Like  other  smuts,  that  of  Corn 
is  capable  of  growing  as  a  saprophyte  in  the  deca3'ing 
vegetable  matter  of  the  soil,  producing  an  abundance  of 
conidia.  It  has  been  found  that  when  the  sporids  or  the 
conidia  germinate  upon  the  meristematic  parts  of  the 
growing  plant  or  the  projecting  styles  of  the  developing 
ears  the}^  penetrate  the  surface  layers,  and  thus  secure 
admission  to  the  tissues  of  their  host. 

408.  Other  Smuts,  as  Wheat  smut  or  Black  Blast 
{Ustilago  tritici)  of  wheat,  Oat  smut  {U.  avenae),  Barley 
smut  ([/.  hordei),  etc.,  have  a  structure  and  mode  of  devel- 
opment closely  resembling  the  foregoing,  but  with  most  of 
these  the  hosts  can  be  infected  only  when  very  young,  i.e. 
during  or  shortly  after  germination,  or  through  their 
stigmas  at  the  time  of  flowering. 

409.  The  Bunt  or  Stinking  smut  of  wheat  {Tilletia 
tritici  and  T.  foelens)  represent  an  allied  family  {Tille- 
tiaceae)  in  which  the  sporids  are  formed  in  a  whorl  at  the 
end  of  the  non-septate  promycelium. 

Laboratory  Studies,  (a)  Collect  specimens  of  cluster  cups 
(from  barberry,  l)uttercups,  or  cvenin<j;  i)riniroses,  etc.);  ex- 
amine first  under  a  low  power  without  niakinfj;  sections.  Note 
the  cups  filled  with  yellowish  or  orange  conidia  (aeciospores). 
Note  spermogones  (minute  dark  spots)  generally  on  the  opposite 
side  of  the  leaf. 

(6)  Make  very  thin  cross-sections  through  a  mass  of  cups  so 
as  to  obtain  vertical  sections  of  the  cups  and  the  spermogones. 

(r)  In  May,  Juno  or  July  collect  leaves  of  wheat,  oats,  or 


238  PHYLU.M  VII.     CARPOMYCETEAE 

barley,  bearing  lines  or  spots  of  Red  rust.  First  examine  a 
few  of  the  spores  mounted  in  alcohol,  with  the  subsequent 
addition  of  a  little  potassium  hydrate.  Then  make  very  thin 
cross-sections  thi-ough  a  rust  si)ot,  and  mount  as  before,  so  as 
to  see  the  parasitic  filaments  in  the  leaf,  bearing  the  Red-rust 
spores  upon  little  stalks. 

(d)  In  July,  August,  or  September  collect  stems  of  wheat, 
oats,  or  barley  bearing  lines  or  spots  of  Black  rust.  Study  the 
teliospores  as  above,  and  afterward  make  cross-sections  also. 

(e)  In  early  spring  collect  and  examine  the  Black  rust  on 
wet  stems  of  rotting  straw.  Look  for  germinating  tehospores 
and  sporids,  which  sometimes  may  be  found. 

(/)  Examine  microscopically  the  gelatinous  prolongations  on 
"cedar-apples,"  and  observe  the  teliospores,  which  resemble 
those  of  Wheat  rust.  *' Cedar-apples,"  which  are  common  in 
the  spring  on  red-cedar  twigs,  are  in  reality  species  of  rust  of 
the  genus  Gymnosporangium.  Their  cluster  cups  occur  on 
apple  leaves.     Uredospores  are  lacking. 

(g)  Collect  smutted  ears  of  Indian  corn.  Mount  a  little  of 
the  black  internal  mass  in  alcohol,  followed  by  weak  potassium 
hydrate  and  observe  the  spores. 

(h)  Make  very  thin  slices  of  young  fresh  or  preserved  speci- 
mens and  examine  for  parasitic  and  spore-bearing  filaments. 
The  outer  tissues  of  the  distorted  kernels  are  generally  best. 

(i)  Make  similar  studies  of  the  smuts  of  wheat,  oats,  or 
barley,  which  may  be  collected  in  June,  or  about  the  time  of  the 
"heading"  of  the  grain. 

(j)  Make  hanging-drop  cultures  (in  water)  of  the  teliospores 
of  Tilletia  and  Ustilago,  and  compare  their  germination. 

The  Imperfect  Fungi 

410.  There  are  many  fungi  (about  16,000  species),  in 
some  respects  resembling  the  Ascus  Fungi  (Ascosporeae), 
of  which  we  know  only  the  conidial  stages.  They  have 
been  brought  together  temporarily  in  three  orders  under 
the  general  name  of  ''Imperfect  F^ungi." 

411.  The  Spot  Fungi  (Order  Sphaeropsidales)  are 
mostly  parasitic  on  leaves  and  fruits  of  higher  plants, 


IMPERFECT  FUNGI  239 

producing  whitish  or  discolored  spots,  and  eventually 
developing  small  perithecia-like  structures  (pycnidia) 
containing  conidia.  Species  of  Phyllosticta  are  common 
on  leaves  of  Virginia  creeper,  wild  grape,  cottonwood, 
willow,  pansy,  peach,  apple,  wild  cherry,  elm,  etc.,  while 
species  of  Septoria  are  to  be  found  on  leaves  of  box-elder, 
aster,  thistle,  evening  primrose,  wild  lettuce,  plum, 
elder,  etc. 

412.  The  Black-dot  Fungi  (Order  Melanconiales) 
differ  from  the  preceding  mainly  in  the  absence  of  a 
distinct  perithecium,  the  spores  developing  beneath  the 
epidermis  of  the  host  and  ])ursting  through  so  as  to  form 


Fig.   115. — Septoria.  Fig.  116. —  Fig.   117. — Cercospora. 

Gloeosporiuni. 

small  dark-colored  or  black  dots  (acervuli).  Species  of 
Gloeosporium  and  Melanconium  are  common  on  leaves, 
fruits,  and  twigs. 

413.  In  the  Molds  (Order  ]Moniliales)  the  conidia- 
bearing  threads  emerge  through  the  stomata  of  the  host, 
or  grow  out  through  the  outer  decaying  tissues,  forming 
moldy  patches  or  masses.  Here  are  many  common 
parasites  (e.g.  species  of  Ramularia,  Cercospora,  Fusi- 
cladium)  and  saprophytes  (Monilia,  Botrytis,  etc.),  some 
of  which  are  l)otli  parasitic  and  saprophytic. 

Laboratory  Studies.  Altliou«2;h  the  Imperfect  Fungi  are 
quite  too  diliicuh  lor  the  beginner  to  do  much  with,  it  is  well 
that  he  should  become  somewhat  familiar  with  their  general 
appearance;  accordingly  a  few  studies  are  suggested. 


240  PHYLU.M  VII.     CARPOMYCETEAE 

(a)  Look  for  Spot  Fungi  on  the  hosts  mentioned  above,  and 
especially  for  the  minute  black  fruits  in  the  spots,  making 
sections  of  the  latter. 

(b)  Look  for  Black-dot  Fungi  on  leaves,  fruits  and  twigs  of 
many  plants,  especially  for  Colletotrichum  on  bean  pods. 

(c)  Look  for  Molds  on  leaves,  as  well  as  on  some  dead 
tissues. 

414.  Summary  for  the  Higher  Fungi.  The  theory 
underlying  the  foregoing  account  of  the  Higher  Fungi  is 
that  these  plants  have  been  derived  from  the  Red  Algae 
by  modifications,  mostly  degradational,  due  to  the  change 
from  a  holophytic  to  a  hysterophytic  habit,  accompanied 
by  the  equally  significant  change  from  aquatic  to  non- 
aquatic  life.  It  is  here  considered  probable  that  the 
earliest  fungi  were  those  known  as  'lichens,"  which 
became  parasitic  upon  small  algae.  In  them  the  dom- 
inant modification  was,  of  course,  the  disappearance  of 
chlorophyll,  and  the  reduction  of  the  plant  body.  In 
the  fruit  resulting  from  the  fertiUzation  of  the  egg,  the 
homologues  of  the  carpospores  of  the  Red  Algae  divided 
internally  into  spores,  thus  changing  the  carpospore 
into  the  ascus,  and  resulting  in  the  considerable  multi- 
plication of  spores.  Thus  the  asci  and  ascospores  be- 
came characteristic  structures  in  the  fruits  of  the  fungi, 
and  gave  name  to  the  first  class — Ascosporeae. 

415.  Later,  in  the  subterranean  fruits  of  the  truffles 
another  modification  took  place  whereby  the  spores 
instead  of  remaining  within  the  ascus,  push  out  beyond 
the  ascus  wall,  so  as  to  be  more  easily  dispersed.  In 
this  way  the  basidium  with  its  basidiospores  arose  from 
the  ascus  and  its  ascospores.  These  are  thus  to  be  re- 
garded as  homologous  structures,  in  which  the  later- 
formed  basidia  have  superior  means  for  dispersing  their 
spores. 

416.  In   like   manner   in   the   Brand   Fungi   we   find 


PHYLOGENY  OF  FUNGI  241 

teliospores  instead  of  the  homologous  ascospores  or 
basidiospores,  and  in  these  plants  the  fruit  body  has 
become  so  reduced  as  to  be  scarcely  recognizable  as  such. 
The  excessive  parasitism  of  these  plants  may  account  for 
their  physical  degeneration.  As  to  the  origin  of  the 
Brand  Fungi  it  is  probable  that  they  came  off  from  the 
parasitic  Ascosporeao  rather  early  in  the  phyletic  history, 
and  a  possible  relationship  is  here  suggested  with  the 
Exoascales,  and  the  Phacidiales. 

417.  The  Imperfect  Fungi  are  thought  to  be  mainly 
Ascosporeae  that  may  have  lost  their  ascospores  through 
excessive  degeneration.  It  is  probable,  however,  that 
many  of  them  are  the  conidial  stages  of  Ascosporeae  and 
Basidiosporeae  whose  relationship  is  not  yet  recognized. 
In  recent  years  many  conidial  forms  hitherto  placed  here 
have  been  found  to  belong  to  well  known  ascigerous 
fungi. 

LITERATURE  OF  CARPOMYCETEAE 

F.  E.  Clements,   The  Genera   of  Fungi,    Minneapolis,    1909. 
P.  A.  Saccardo,  Sylloge  Fungorum,  Vols.  I  to  XXII,  1882-1913. 
These  are  comiDrehensive  works;  the  following  include  certain 
portions  of  the  Higher  Fungi. 
J.  B.  Ellis  and  B.  M.  Everhart,  North  American  Pyrenomy- 

cetes,  Newfield,  1892. 
Bruce  Fixk,  Lichens  of  Minnesota,  Washington,  1910. 
Albert  Schneider,  A  Text-hook  of  Lichenulogy,  Binghainton, 

1897. 
L.    M.    Underwood,    Molds,  Mildews  and  Mushrooms,  Xew 

York,  1899. 
C.  B.  Plowrioiit,  .1   Monograph  of  the  British  Uredineae  and 
Ustilagincaea,  London,  1889. 


16 


CHAPTER  XIV 

PHYLUM  VIII.     BRYOPHYTA 

THE  MOSSWORTS 

418.  This  phylum  includes  plants  of  much  greater 
complexity  than  any  of  the  preceding.  In  very  many 
cases  they  have  distinct  stems  and  leaves,  whose  tissues 
often  show  a  differentiation  into  several  varieties.  In 
the  sexual  organs  the  cell  to  be  fertilized  (the  egg)  is  from 
the  first  enclosed  in  a  protective  layer  of  cells,  and  after 
fertilization  it  develops  into  a  complex  spore-bearing 
body. 

419.  The  life-cycle  of  the  Mossworts  includes  a  dis- 
tinct alternation  of  generations.  The  immediate  prod- 
uct of  the  fertilization  of  an  egg  is  not  a  thalloid  or  leafy 
plant  Uke  that  which  bears  the  sexual  organs,  but,  on  the 
contrary,  it  is  a  many-celled  leafless  structure,  spherical 
or  approximately  cylindrical,  which  eventually  produces 
spores  internally.  The  plant  which  produces  the  sexual 
organs  is  the  gametophyte,  while  that  which  produces  the 
spores  is  the  sporophyte. 

420.  So  the  Mossworts  have  a  marked  duality,  and  we 
must  consider  both  phases  when  we  wish  to  get  a  complete 
idea  of  any  particular  plant.  This  duality  has  permitted 
the  acquisition  of  the  land  habit,  since  the  gametophytes 
have  retained  some  of  their  aquatic  characteristics,  while 
the  sporophytes  have  become  modified  for  a  terrestrial 
life.  Accordingly  in  Bryophytes  we  find  the  beginning  of 
the  terrestrial  habit  in  green  plants. 

242 


ALTERNATION  OF  GENERATIONS  243 

421.  Mossworts  may  then  be  described  as  green  plants 
in  which  the  gametophyte  is  a  prostrate  or  erect  some- 
what long-Hvcd  phint,  producing  antherids,  and  oogones 
(the  latter  enclosed  in  archegones).  After  fertilization  a 
distinct  structure,  the  sporophyte,  is  produced,  but  al- 
though it  rests  on  and  in  the  gametophyte  and  obtains  its 
supply  of  water  and  much  of  its  food  from  it  there  is 
no  organic  connection  between  them.  In  this  sporo- 
phyte certain  internal  cells  (the  ''spore  mother-cells") 
divide  twice  and  thus  produce  internally  four  spores 
each.  These  eventually  germinate  and  produce  other 
gametophytes. 

422.  Here  it  should  be  noted  that  the  nuclei  of  the 
gametophyte  cells  contain  a  definite  number  of  chromo- 
somes, and  that  on  the  fertilization  of  the  egg  this  number 
is  doubled.  This  double  number  is  maintained  in  the 
sporophyte  until  spores  are  formed  by  division  into  fours, 
at  which  time  a  reduction  takes  place  to  the  original  num- 
ber. So  in  this  phylum  the  two  generations  are  separable 
also  by  their  chromosome  numbers  in  addition  to  the 
other  more  obvious  differences. 

423.  The  antherids  are  complex  structures.  They  are 
usually  short-stalked,  and  consist  of  a  layer  of  large 
])Oundary  cells  within  which  are  very  numerous,  small, 
more  or  less  cu])ical  cells,  each  of  which  produces  in- 
ternally an  elongated,  more  or  less  spiral,  biciliate  sperm. 
The  walls  of  these  spermatogenous  cells  dissolve,  leaving 
the  sperms  free  within  the  cavity  of  the  antherid.  By  the 
rupture  of  the  apical  cells  the  sperms  escape.  This 
occurs  only  when  the  antherid  is  covered  with  water  (rain, 
dew,  etc.). 

424.  The  archegone  is  a  flask-shaped,  elongated  organ, 
consisting  of  an  enlarged  lower  part  (venter)  containing 
the  egg,  aljove  which  is  the  slender  neck,  at  first  closed  at 


244  PHYLUM  VIII.     BRYOPHYTA 

the  top  and  surrounding  the  row  of  canal  cells,  but  later 
open  with  a  continuous  passage  to  the  egg  (owing  to  the 
dissolution  of  the  canal  cells).  In  fertilization  which 
takes  place  in  water,  the  sperms  pass  down  the  tubular 
neck  to  the  egg  below. 

425.  Mossworts  are  of  small  size,-  rarely  exceeding  10  or 
15  centimeters  in  height.  They  generally  prefer  moist 
situations  upon  the  ground,  or  on  the  sides  of  trees  or 
rocks.  All  told  there  are  somewhat  more  than  16,000 
species.     Two  classes  may  be  distinguished,  as  follows: 

Mostly  bilateral,  often  thalloid,  creeping  gametophytes, 
usually  with  splitting  sporophytes,  and  mostly  having 
elaters Class  Hepaticae. 

Multilateral,  leafy -stemmed,  mostly  erect  gametophytes,  usu- 
ally with  circularly  dehiscing  sporophytes,  and  without 
elaters Class  IMusci. 


Class  HEPATICAE.     Liverworts 

426.  In  the  lower  Liverworts  the  gametophy te  is  a  flat, 
expanded  thallus  of  parenchymatous  tissue,  and  this 
gradually  differentiates  into  a  leafy  stem  as  we  pass  to 
the  higher  forms,  but  in  all  cases  the  plant  body  has  two 
distinct  and  well-marked  surfaces,  an  upper  and  an  under 
one,  the  latter  bearing  the  root-hairs  (rhizoids)  by  which 
the  plant  is  fixed  to  the  ground.  About  4000  species  are 
known. 

427.  Among  the  simplest  of  the  Liverworts  are  the 
little  round,  flat  Riccias  (Riccia)  which  grow  on  wet  earth 
or  even  float  on  the  water.  In  the  upper  surface  of  the 
loose  green  tissue  are  the  sunken  antherids  which  pro- 
duce biciliated  spiral  sperms.  In  a  similar  manner  the 
archegones  are  sunken  in  the  upper  surface.  After  fer- 
tilization the  egg  develops  into  a  globose  cellular  body 


HORXWORTS 


245 


(the  sporophyte),  whose  interior  cells  divide  into  spores, 
hut  there  are  no  "  elaters."  Although  still  surrounded  by 
the  distended  archegone  this  sporophyte  is  not  organically 
connected  with  any  part  of  the  gametophyte.  The  spores 
escape  by  the  decay  of  the  surrounding  layers  of  cells,  and 
on  germination  give  rise  to  gametophytes  like  that  with 
which  we  started. 

428.  In  the  Horn  worts  (Anthoceros)  the  gametophyte 
is  a  thin  thallus  of  somewhat  more  compact  tissue  than 
in  Riccia,  and  growing  on  moist  earth.     The  antherids 


Fig.   lis.— Rice 


Fig.   119. 


Anthoceros. 


and  archegones  are  sunken  in  the  upper  surface,  and 
resemble  those  of  Riccia.  When  fertiUzed  the  egg  de- 
velops into  an  elongated,  cylindrical  sporophyte  whose 
upper  part  emerges  from  the  neck  of  the  archegone, 
while  the  enlarged  base  remains  seated  in  the  venter. 
The  sporophyte  is  made  up  of  a  considerable  mass  of 
green  tissue,  and  is  surrounded  by  an  epidermis  which  is 
suppUed  with  stomata  like  those  of  higher  plants.  This 
the  first  appearance  of  true  stomata  in  the  Vegetable 
Kingdom. 

429.  The  lower  part  of  the  sporophyte  continues  to 
grow  in  length  indefinitely.  Internally  there  is  a  layer 
of  cells  by  the  division  of  which  spores  are  formed,  and 
intermingled  with  these  spores  are  the  elongated  sterile 
cells  called  ''elaters. ''  As  the  spores  ripen  above  the 
sporophyte  splits  from  the  top  to  permit  their  escape. 


246 


PHYLUAI  VIII.     BRYOPHYTA 


Fig.      120. — Marchantia, 
brood-masses  (gemmae). 


On  germination  the  spores  produce  gametophytes  like 
the  originals. 

430.  The  verj^  conspicuous  Great  Liverwort  (Mar- 
chantia) is  common  on  moist  ground  and  is  frequently 
abundant  in  green  houses.  Its  gametophyte  is  a  large, 
flat,  branching,  thalloid  plant  with  a  distinct  midrib. 
Its    epidermis    is    pierced    with    circular,    many-celled 

''stomata"  which  open  into  large 
air  cavities  supplied  with  many 
green  cells.  Here  and  there  on  the 
upper  surface  are  cups  containing 
hairs  whose  terminal  cells  develop 
into  green  masses  (brood  masses,  or 
gemmae)  which  fall  off  and  quickly 
develop  into  new  gametophytes.  This  is  thus  an  asex- 
ual mode  of  reproduction,  and  these  brood  masses  take 
the  place  of  the  zoospores,  tetraspores, 
and  conidia  of  lower  plants. 

431.  The  antherids  are  confined  to  par- 
ticular portions  of  the  gametophyte  (an- 
theridial  disks)  which  are  raised  on  short 
stalks.  Here  they  are  sunken  in  the  sur- 
face and  they  and  the  sperms  resemble 
those  of  Riccia  and  Anthoceros. 

432.  The  archegones  are  also  confined  to  particular 
portions  of  the  gametophyte  (known  as  '^ receptacles" 

but  really  lobed  disks)  which  are  raised 
on  more  or  less  elongated  stalks  (arche- 
gonial  branches).  The  archegones  are 
dependent  from  the  under  side  of  the  re- 
ceptacle. When  fertilized  the  egg  de- 
velops into  a  globose,  shortly  stalked 
sporophyte  containing  spores  and  elon- 
gated sterile  cells,  the  "elaters,"  whose  walls  are  spirally 


Fig.  121.— March- 
antia (antherids). 


Fig.   122.— March 
antia  (archegones) 


SCALE  MOSSES  247 

thickened.  By  the  expansive  force  of  these  elaters 
the  sporophyte  is  ruptured  somewhat  stellately,  and  the 
spores  are  forced  out.  When  the  spores  germinate  they 
give  rise  directly  to  the  f!;ametophyte  generation. 

433.  The  Scale  mosses  (Order  Jungermanniales) 
are  the  highest  of  the  Liverworts,  and  also  the  most 
numerous  in  species.  In  the  lower  family  {Metz- 
gcriaccae)  the  gametophyte  is  usually  a  thal- 
lus  as  in  the  liverworts  already  described, 
but  in  the  higher  family  {J linger manniaceae) 
it  is  a  creeping,  leafy  stem.  In  the  first 
f amity  w^e  find  all  gradations  from  the  en-  p^^  12.3  — 
tire  margined  thallus  to  those  with  more  and-  Metzgeria,  and 

^  Jungermanma. 

more  pronounced  lateral  lobing,  and  finally 
to  those  in  which  the  lobes  have  become  distinct  leaves 
on  a  rounded  stem.     The  leaves  of  Scale  mosses   are 
but  one  cell  thick  and  are  not  ribbed. 

434.  The  antherids  and  archegones  are  borne  dorsally 
or  subterminally  and  are  much  like  those  already 
described.  The  sporophyte  develops  a  slender  stalk 
which  carries  up  the  enlarged  spore  case,  and  the  latter 
when  the  spores  are  mature  splits  vertically  into  four 
segments  and  permits  the  escape  of  spores  and  elaters. 
When  the  spores  germinate  they  may  develop  directly 
such  adult  gametophytes  as  are  described  above,  while 
in  the  higher  forms  the  gametophyte  is  first  a  filamentous 
or  thalloid  structure  ('^protonema")  from  which  tlie 
adult  gametophyte  subsequentl}^  buds  out. 

435.  ALmy  Scale  mosses  reproduce  by  means  of  l^rood 
masses  much  like  those  of  Marchantia,  or  even  simple, 
single-celled  structures  (brood  cells). 

436.  Scale  mosses  have  no  stomata  on  either  gameto- 
phytes or  sporophytes. 


248  PHYLUM  VIII.     BRYOPHYTA 

Laboratory  Studies,  (a)  Look  for  Riccias  on  the  wet 
ground  by  the  sides  of  ponds  and  slow  streams  from  midsummer 
to  fall.  Make  careful  vertical  sections  for  structure  of  the 
gametophyte,  at  the  same  time  looking  for  the  sexual  organs 
and  the  imbedded  sporophyte. 

(b)  Study  Anthoceros  for  gametophyte,  and  cylindrical  spor- 
ophj'tes.  In  the  latter  find  stomata,  spores  and  simple  elaters. 
Anthoceros  may  be  obtained  from  the  South  (Gulf  states)  for 
study  in  early  spring. 

(c)  Collect  specimens  of  the  Great  Liverwort  (Marchantia) 
which  may  be  found  in  fruit  in  midsummer.  Note  that  one 
plant  produces  the  antheridial  branches,  which  have  flat  disks, 
and  another  produces  the  archegonial  branches,  which  have 
lobed  disks  (''receptacles").  Note  the  cups,  with  contained 
brood  masses  (gemmae). 

(d)  Examine  the  upper  surface  of  a  plant  with  a  low  power 
of  the  microscope,  and  note  the  round  ''stomata."  Next  strip 
off  some  of  the  epidermis,  mount  in  alcohol,  and  study  with  a 
high  power. 

(e)  Make  longitudinal  sections .  of  the  plant  through  its 
thickened  central  rib,  and  observe  the  elongated  cells,  with 
foreshadow  fibro-vascular  bundles. 

(/)  Make  vertical  sections  of  the  antheridial  disk,  mount  in 
water,  and  study  the  antherids.  By  repeated  trials  sperms 
also  may  be  seen. 

(g)  Make  similar  sections  of  the  archegonial  disk,  and  study 
archegones.  By  taking  older  specimens  the  sporophytes, 
spores,  a<nd  elaters  may  be  studied.  For  the  latter,  mount  in 
alcohol  and  afterward  add  a  little  potassium  hydrate. 

(h)  Examine  the  bark  of  trees  for  small  brownish  Scale 
mosses.  Mount  a  bit  of  one  in  alcohol,  afterward  adding  potas- 
sium hydrate,  and  study  for  structure  of  the  gametophyte. 
In  the  spring  the  minute  splitting  spore  cases  may  readily  be 
found. 

Class  MUSCI.  Mosses 

437.  The  gametophyte  in  this  class  is  a  leafy  multi- 
lateral stem,  rarely  bilateral.  It  is  fixed  to  the  soil  or 
other  support  by  root-hairs  (rhizoids)  which  grow  out 
from   the   sides  of  the  stem.     The  leaves  are  usually 


MOSSES  249 

composed  of  a  single  layer  of  cells,  and  in  many  cases  have 
a  midrib.  The  sporophyte  is  more  or  less  elongated, 
enlarged  above  into  a  spore-case  (capsule)  and  does  not 
contain  claters. 

438.  The  tissues  of  the  Mosses  present  a  considerable 
advance  upon  those  of  the  Liverworts.  In  the  stem 
there  is  frequently  a  bundle  of  very  narrow  thin-walled 
cells,  which  in  some  species  become  considerably  thick- 
ened. In  a  few  cases  there  have  been  observed  bundles 
of  thin-walled  cells  extending  from  the  leaves  to  the 
bundles  in  the  stem.  It  cannot  be  doubted,  then,  that 
the  Mosses  possess  rudimentary  fibro-vascular  bundles. 
As  in  liverworts,  the  tissues  of  mosses  develop  from 
a  single  apical  cell.  Breathing-pores  (stomata)  re- 
sembling those  of  the  higher  plants  occur  on  the  sporo- 
phytes;  they  are  not  found  upon  the  leaves  or  stems. 

439.  Mosses,  for  the  most  part,  grow  upon  moist 
earth  or  rocks,  or  upon  the  trunks  and  branches  of 
trees;  comparatively  few  are 
aquatic.  They  range  in  size  from 
less  than  a  millimeter  to  many 
centimeters  in  length,  the  most 
common  height  being  from  2  to  4 
centimeters.  They  are  all  chlo-  fig.  124.-A  moss  (protonema 
rophyll-bearing   plants,    and    are       and  leafy  gamctophyte). 

generally  of  a  bright  green  color;  occasionally,  however, 
they  are  whitish  or  brownish. 

440.  The  reproduction  of  mosses  is  mainly  sexual, 
but  often  brood-masses  are  found  resembling  those  of 
liverworts.  The  sexual  organs  develop  either  upon  the 
ends  of  the  main  stems,  within  flower-like  rosettes  of 
leaves,  or  on  the  ends  of  short  branches  in  the  axils  of  the 
leaves. 

441.  The  antherids  are  club-shaped  or  gloi)ose  struc- 


250  PHYLUiM  VIII.     BRYOPHYTA 

tures  whose  interior  cells  produce  sperms,  which  escape 
from  the  antherid  through  a  rent  in  its  wall.  Each 
spermatogenous  cell  contains  one  spirally  coiled  sperm, 
which,  when  set  free,  swims  by  means  of  its  two  long  cilia. 
442.  The  archegones  are  elongated,  flask-shaped  bodies 
with  a  swollen  base  (''venter")  and  a  long  slender 
neck.  At  maturity  the  neck  has  an  open  channel  from 
its  apex  to  the  base,  where  there  is  a  rounded  egg.  In 
some  mosses  the  antherids  and  archegones  are  inter- 
mixed in  the  same  "flower,"  but  in  other  cases  they 
occur  upon  different  parts  of  the  same  plant  (  monoe- 
cious), or  even  upon  different  plants  (dioecious). 


Fig.   125. — Antherids  and  Fio.   126. — Archegones  and  eggs 

sperms      (Sphagnum      and  (Sphagnum  and  Funaria). 

Funaria). 

443.  The  act  of  fertilization  requires  water;  but  as  the 
sperms  are  very  minute,  a  dewdrop  may  be  suflacient. 
The  sperms  swim  to  the  open  neck  of  the  archegone, 
down  which  they  pass  to  the  egg.  The  egg  now  begins 
to  divide  rapidly,  growing  upward,  eventually  forming 
the  sporophyte.  In  most  mosses  the  sporophyte  is 
narrow  and  elongated  below,  forming  a  stalk  (seta) 
which  supports  the  upper  spore-bearing  part  (the  capsule 
or  spore-case).  The  epidermis  of  the  latter  is  usually 
provided  with  stomata,  especially  toward  its  basal  part. 

444.  The  spore-case,  when  ripe,  usually  opens  by  a 
lid  which  falls  off,  leaving  a  round  opening,  generally 
fringed  with  many  teeth.     In  most  species  as  the  sporo- 


I 


ORDERS  OF  MOSSES  251 

phyto  elongates  it  carries  up  the  remains  of  the  distended 
archegone  as  a  Uttle  cap  (calyptra). 

445.  The  spores,  which  are  round  or  angular  cells 
containing  protoplasm,  chloroplasts,  oil-drops,  etc., 
germinate  quickly  upon  moist  soil.  Each  spore  pro- 
trudes a  tubular  filament,  which  develops  into  a  conferva- 
like ])ranching  growth  of  green  cells,  called  the  '^pro- 
tonema."  Upon  this  buds  are  event uall}^  produced  from 
which  spring  up  the  leafy  stems,  thus  completing  the 
round  of  life. 

446.  There  are  three  orders  of  Mosses,  including  about 
12,600  species,  as  follows:  (1)  Black  Mosses  (Order  An- 
dreas ales),  composed  of  a  few  small  and  rare  mosses 
whose  spore-cases  open  by  four  longitudinal  slits;  (2) 
Peat-mosses  (Order  Sphagnales),  composed  of  large, 
soft  and  usually  pale-colored  plants,  with  clustered  lat- 
eral branches;  they  inhabit  bogs  and  swamp}-  places, 
where  they  form  dense  moist  cushions,  often 
of  great  extent.  On  account  of  pecuharities 
in  the  structure  of  their  leaves  they  are  en- 
abled to  absorb  and  hold  large  quantities  of 
water,  and  for  this  reason  they  are  exten- 
sively used  for  "packing"  in  the  transporta- 
tion of  living  plants.  They  all  belong  to  Fig.  127  — 
the  genus  Sphagnum,  and  their  spore-cases  (Amirt<aeu  and 
open  by  a  circular  lid,  leaving  an  unguarded 

opening  (without  teeth).  In  this  and  the  preceding 
order  the  stalk  supporting  the  spore-case  is  an  extension  of 
the  gametophyte  stc^n  and  not  a  part  of  the  sporophyte. 

447.  (3)  True  Mosses  (Order  Bryales)  include  the 
great  majority  of  the  species  of  this  class.  They  are 
usually  bright  green  (in  a  few  genera  brownish),  and  in 
most  instances  live  upon  moist  ground  and  rocks,  or 
upon  the  bark  of  trees;  in  a  comparatively  small  number 


252  PHYLUM  VIII.     BRYOPHYTA 


/^ 


of  cases  the  species  live  in  the  water.  They  are  undoubt- 
edly the  highest  of  the  class,  and  show  a  greater  differ- 
entiation of  tissues  than  either  of  the  pre- 
ceding orders.  The  spore-cases  usually 
r^  open  by  a  circular  lid  (operculum),  and 
'  V  the  opening  is  usually  guarded  by  one  or 
_  two  rows  of  teeth  (the  peristome)  of  which 
Sporophytea  there  may  be  4,   8,    16,  32  or  64.     Here 

(Bryales).  ^  \      ^  i       . 

the  seta  is  a  part  of  the  sporopnyte. 
448.  There  are  more  than  fifty  families  of  True 
Mosses,  of  which  about  one-half  are  Top  Mosses 
(Acrocarpi),  i.e.  bearing  their  sporophytes  at  the  summit 
of  the  gametophyte  stem,  the  remainder  being  Side 
Mosses  (Pleurocarpi) ,  with  laterally  borne  sporophytes. 
Among  the  first  are  Turf  Mosses  (Dicranaceae) ,  Cushion 
Mosses  (Leucohryaceae) ,  Petticoat-mosses  \> 
(Splachnum) ,  Bristle  Mosses  {Funariaceae 
and  Timmiaceae)  y  Ephemeral  Mosses  {Ephe- 
merum),  Wood  Mosses  (Bryaceae  and  Mnia- 
ceae),  Humpback  Mosses  {Buxhaumiaceae) , 
and  Hair-cap  Mosses  (Po^y^nc/iaceae) .  Among  Top  "  moss, 
the  Side  Mosses  are  the  Brook  Mosses  [b  on- 
tinalaceae),  the  Tree  Mosses  {Climaciaceae) ,  and  the  Bog 
Mosses  (Hypnaceae). 

Laboratory  Studies,  (a)  Collect  several  kinds  of  mosses  in 
fruit;  some  of  these  should  be  of  large  species.  Note  the 
brownish  root-hairs,  the  stem  and  leaves,  the  spore-fruit  (sporo- 
phyte)  composed  of  a  slender  stalk  (seta)  bearing  a  spore-case, 
the  latter  in  some  species  covered  by  a  membranous  or  hairy 
cap  (calyptra). 

(6)  Select  a  broad-leaved  species.  Mount  a  single  leaf  in 
water,  and  examine  with  a  lower  power.  Note  that  the  leaf 
is  (generally)  a  single  layer  of  cells,  and  that  the  midrib  (if 
present)  is  composed  of  elongated  cells.  Make  cross-  and 
longitudinal  sections  of  stems  of  the  larger  species,  and  note 
that  some  of  the  cells  are  elongated  and  fiber-like. 


LABORATORY  STUDIES  253 

(c)  Place  a  spore-case  under  tlic  microscope  and  examine 
with  a  low  power,  noting  the  lid.  Now  remove  the  lid  and 
observe  the  teeth.  The  teeth  may  be  studied  still  better  by 
splitting  the  spore-case  from  base  to  apex  and  then  mounting 
in  alcohol,  and  afterward  adding  potassium  hydrate:  or  the 
lid  may  be  removed  and  a  transection  of  the  si)ore-case  made 
just  below  the  peristome,  so  as  to  show  the  latter  from  above. 
In  these  specimens  spores  may  be  studied  also. 

{(I)  Split  a  young  spore-case  and  examine  the  external  sur- 
face of  the  lower  part  for  breathing-pores,  and  note  internally 
the  adjacent  chlorophyll  tissues,  and  the  sporogenous  layer 
above. 

(e)  Collect  a  number  of  mosses  not  in  fruit,  showing  at  the 
apex  of  their  stems  little  cup-shaped  whorls  of  leaves.  IVIake 
several  vertical  sections  of  one  of  these  cups,  and  mount  in 
water.  Examine  for  antherids  and  archegones.  Sperms  may 
sometimes  be  seen  with  a  high  power. 

(/)  The  first  stage  (protonema)  of  a  moss  gametopl\vte  may 
be  found  by  scraping  off  some  of  the  greenish  growth  from  a  wall 
or  cliff  or  surface  of  a  greenhouse  flower  pot  where  yomig  mosses 
are  just  springing  up.  By  mounting  some  of  this  in  water  and 
washing  awaj^  the  dirt  the  branching  green  growth  may 
generally  be  seen,  with  here  and  there  the  buds  which  give  rise 
to  leafy  stems. 

LITERATURE  OF  BRYOPHYTA 

D.  H.  Campbell,  The  Structure  and  Development  of  Mosses  and 
Ferns,  New  York,  1905. 

L.  AI.  Underwood,  Descriptive  Catalogue  of  the  Xorth  American 
Hepaticae,  Champaign,  1883. 

L.  Lesquereux  and  T.  P.  James,  Manual  of  the  Mosses  of 
North  America,  Boston,  1884. 

A.  J.  Grout,  Mosses  with  a  Hand  Lens  and  Microscope,  Brook- 
lyn, 1905-1911. 


CHAPTER  XV 

PHYLUM  IX.     PTERIDOPHYTA* 

THE  FERNS 

449.  The  Ferns  are  green  plants  that  as  to  their 
gametophytes  are  of  smaller  size  than  the  INIossworts, 
while,  as  to  their  sporophytes  they  are  much  larger  and 
more  complex.  In  fact  the  gametophyte  generation  is 
so  small  compared  with  the  sporophyte  that  it  is  usually 
overlooked,  or  when  seen  is  often  not  recognized  as  a 
fern  at  all  by  those  who  are  not  familiar  with  the  whole 
life  cycle  of  these  plants.  The  fern  that  we  commonly 
see  with  its  roots,  solid  stems,  and  ample  leaves  is  the 
sporophyte  generation,  which  has  become  so  large  and 
conspicuous  in  this  phylum  that  it  completely  over- 
shadows the  little  gametophyte. 

450.  The  gametophyte  (commonly  called  the  ''pro- 
thallium")  is  usually  a  flat  thallus,  of 
one  or  more  layers  of  nearly  uniform 
chlorophyll-bearing  cells,  the  whole 
being  rounded  or  heart-shaped  in  out- 
line.    Its  longitudinal   axis  is  consider- 

FiG.  130.— Game-    ably  thickeued,  and  this  portion  is  pro- 

tophytes"  7  i  i 

vided  underneath  with  many  root-hairs, 
intermingled  with  which  in  most  cases  are  the  antherids 
and  the  archegones. 

451.  The   antherids   are  nearly   globular,   few-celled 

*  This  name  is  here  used  in  the  narrower  sense  excluding  Cala- 
mites  and  Lycopods. 

254 


FERN  STRUCTURE 


:oo 


Fig.   131.— Fern  arch- 
1  r    ,^  • ,  .  ,  1       egone,  egg,  antherid  and 

where  one  oi  them  unites  with  sperm. 


structures  consisting  of  an  outer  hi^-er  of  cells  surrounding 
a  central  mass  of  small  cells,  each  of  which  produces 
a  sperm.  When  mature,  the  antherids  rupture  and 
permit  the  escape  of  the  spiral  multiciliated  sperms 
which  swim  with  a  rotary  motion. 

452.  The  archegones  are  flask-shaped  organs  sunken 
into  the  tissues  of  the  plant.  At  first 
the  neck  is  closed,  but  at  maturity  it 
opens  down  to  the  egg.  Fertilization 
takes  place  in  water  (after  rains  or 
heavy  dews),  the  sperms  swimming 
to  and  down  the  neck  of  the  arche- 
gone, 
the  egg. 

453.  Sporophyte.  After  fertilization  the  egg  divides 
again  and  again,  soon  producing  a  solid  stem  from  which 
a  root  springs  at  one  end,  while  from  the  other  the  leaves 
arise.  The  latter  are  at  first  small  and  quite  simple  in 
structure,  but  those  formed  later  are  larger  and  more 
and  more  complex  in  structure,  until  finally  the  full  form 

is  reached,  and  still  later  the  full 
size.  The  stem,  bearing  leaves 
and  roots,  constitutes  the  sporo- 
phyte, which  is  sharply  contrasted 
with  the  gametophyte  in  structure, 
size,  and  duration,  the  latter  being 
short-lived,  small,  and  of  simple 
structure,  while  the  former  is  long-lived,  often  of  large 
size,  and  of  great  complexity  of  structure.  On  this 
plant  the  spores  are  eventually  produced  which  on 
germination  give  rise  to  gametophytes  like  those  with 
which  we  started,  thus  completing  the  round  of  life.  In 
most  Ferns  the  spores  are  of  one  kind,  only  (isospores), 
but  in  a  few  they  are  of  two  kinds  (heterospores)   in 


<M^'^ 


Fig 


132. — Development  of 
fern  sporophyte. 


256  PHYLUM  IX.     PTERIDOPHYTA 

which  some  arc  small  (microspores)  and  the  others  large 
(megaspores). 

454.  In  looking  over  the  whole  structure  of  the  Ferns 
it  will  be  seen  that  the  sporophyte  has  become  the 
dominant  generation.  This  is  due  to  the  fact  that  in 
its  development  it  has  pushed  roots  of  its  own  down  into 
the  ground  from  its  lower  end,  thus  insuring  a  constant 
supply  of  water,  while  at  the  same  time  it  has  pushed 
out  some  of  the  green  tissue  from  its  upper  part  into  flat 
expansions  (leaves),  thus  insuring  the  supply  of  car- 
bohydrates. The  sporophyte  has  thus  become  in- 
dependent of  the  gametophyte,  and  the  latter,  being  now 
useless  after  the  maturity  and  disappearance  of  the  sexual 
organs,  has  become  very  short-lived,  while  the  rooted 
and  leafy  sporophyte  has  developed  into  a  long-lived 
plant,  which  may  continue  its  growth  for  many  years. 

455.  With  this  longer  life  and  larger  size  the  fern 
sporophytes  have  developed  many  kinds  of  tissues  in 
addition  to  parenchyma,  including  collenchyma,  scler- 
enchyma,  fibrous  tissue,  tracheary  tissue,  and  sieve 
tissue,  some  of  which  appear  to  be  as  highly  specialized 
as  in  the  flowering  plants.  Furthermore,  true  vascular 
bundles  as  well  as  bundles  of  fibrous  tissue  are  developed, 
the  roots  containing  bundles  of  the  radial  type,  and  the 
solid  stems  and  leaves,  of  the  concentric  tj^pe.  The 
epidermis  and  stomata  are  scarcely  to  be  distinguished 
from  those  of  the  highest  plants. 

456.  The  typically  large  leaves  are  sometimes  simple, 
flat  blades,  but  more  commonly  they  have  branched  into 
*' compound"  blades  of  extraordinary  complexity  and 
beauty  of  outline.  The  young  leaves  before  expanding 
are  generally  coiled  or  rolled,  so  that  as  they  grow  up 
and  open  they  unroll  from  below  upward  (i.e.  cir- 
cinately).     Their  vascular  bundles  (here  usually  called 


OLD-FASHIONED  FERNS  257 

''veins")  present  different  patterns,  sometimes  being 
parallel  to  one  another  or  divergent  (veins  ''free"),  or 
uniting  here  and  there  in  a  netted  fashion  (veins 
"reticulated"). 

457.  Since  the  sporophytes  of  ferns  are  long-lived 
the}"  delay  the  formation  of  their  spores,  this  sometimes 
not  taking  place  for  a  few  years  (or  many  years  in  tree 
ferns).  In  the  more  primitive  ferns  the  spores  develop 
from  internal  cells  (as  in  Anthoceros  of  the  Bryophyta), 
but  in  the  higher  forms  they  are  produced  in  superficial 
sporangia. 

458.  On  account  of  the  dominance  of  the  sporophyte 
its  structure  has  been  emphasized  in  the  s^^stematic 
classification  of  the  ferns,  although  some  consideration 
has  latterly  been  given  to  gametophyte  characters. 
About  3800  species  of  Ferns  have  been  described,  and 
they  are  widely  distributed  throughout  warm  and  tem- 
perate regions. 

459.  There  are  two  classes  of  Ferns,  as  follows: 
1.  Old-fashioned  Ferns  (Class  Eusporangiatae)  in  which 
the  spores  develop  from  internal  cells. 


Fig.   133. — Ophioglossuni.  Fig.   134. — Angiopteria 

(Marattialcs);     develop- 
ment of  sporangia. 

460.  Here  are  the  Adder-tongues  (Order  Opiiio- 
GLOSSALEs)  by  many  botanists  regarded  as  the  lowest  of 
the  Ferns,  and  not  very  distantly  related  to  Anthoceros 
of   the   preceding   phylum.     Here   too   are   placed   the 

17 


258  PHYLUM  IX.     PTERIDOPHYTA 

Marattias  (Order  Marattiales),  large,  very  leafy  ferns 
of  the  tropics,  formerly  abundant,  now  nearly  extinct, 
and  with  them  may  be  placed  the  aquatic  Quillworts 
(Order  Isoctales)  with  slender  rush-like  leaves.  The 
latter  produce  two  kinds  of  spores,  viz.  microspores 
which  are  small,  and  megaspores  which  are  much  larger. 
The  plants  are  thus  heterosporous,  in  contrast  with 
the  preceding  which  are  isosporous.  The  microspores 
produce  minute  antheridial  gametophytes  (microgame- 
tophytes),  and  the  megaspores,  larger  archegonial 
gametophj'tes  (megagametophy tes) . 

2.  Modern  Ferns  (Class  Leptosporangiatae)  develop 
their  sporangia  from  superficial  cells. 

461.  These    are    our    common   ferns,    and    this    class 
includes  the  greater  part  of  the  species  now  living.     In 
them  the  sporangia  are  usually  developed  on  the  lower 
surface  of  the  leaves  in  clusters  (''  sori ")  of  various  shapes, 
and   these   may   be  naked   or  covered 
with  an  indusium.     The   mature  spor- 
angium (spore-case)  in   most  common 
ferns    has    a    ring  of  thicker  cells  ex- 
tending   around    it.      When   these  be- 
come (hy,  they  contract  in  such  a  way 
„      ,^,     ,,  ,       as  to   break    open   the  spore-case  and 

Fig.     13o. — Modern  ^  ^ 

ferns  (sporangium  and  thus  sct  the  sporcs  free.     Most  Modcm 

son).  '■ 

Ferns  are  terrestrial,  and  hence  may 
be  set  off  as  Land  Ferns  (Order  Fili gales),  in  which 
are  the  less  common  CHmbing  Ferns  (Lygodium),  Tree 
Ferns  (FsunWy  Cyatheaceae) ,  Filmy  Ferns  (Family //?//rteno- 
phyllaceae),  and  Common  Ferns  (Family  Polypodiaceae). 
In  the  last-named  family  nearly  all  of  the  ferns  of  our 
woodlands  are  found,  including  such  species  as  the 
common  Polypody  (Polypodiiim  vulgare),  the  Golden 
Fern    of    California    {Gymnograrnme    triangularis),    the 


WATER  FERNS  259 

Maidenhair  of  the  North  {Adiantum  pedatum),  and  of 
the  South  {A.  capillus-ve?ieris) ,  the  common  Brake 
{Pteridium  aquilinum)  the  Spleenworts  (Asplenium)  of 
many  species,  the  Shield-ferns  (Aspidium),  also  of  many 
species,  the  curious  little  Walking- fern  {Camptosorus 
rhizophyllus),  the  Bladder-fern  (Filix  fragilis)  and  the 
large  Ostrich-fern  {Onoclea  struthiopteris) . 

462.  Some  of  the  Modern  Ferns  have  become  aquatic 
and  hence  are  known  as  Water  Ferns 
(Order  Marsiliales)  in  which  two  kinds  of 
spores  ("heterospores")  are  produced,  mic- 
rospores and  megaspores,  which  in  time  give 
rise  respectively  to  antheridial,  and  arch- 
egonial  gametophytes.  The  Marsilias  are 
rooted  plants,  with  floating,  4-parted  leaves, 
while  the  Salvinias  are  small,  floating,  nearly  rootless 
plants,  with  simple  leaves. 

Laboratory  Studies,  (a)  Collect  several  different  kinds  of 
common  ferns,  including  the  underground  portions  as  well  as 
the  leaves.  Study  the  vascular  bundles,  stone  tissue,  and 
fibrous  tissue  in  the  underground  stem. 

(6)  Examine  the  disposition  of  the  small  vascular  bundles  in 
the  leaves,  whether  free  or  reticulated.  Peel  off  a  bit  of  epider- 
mis from  both  surfaces,  and  study  the  breathing-pores. 

(c)  With  a  low-power  study  the  sori  (clusters  of  spore-cases), 
using  top  light  only.  The  sporangia  maj^  be  seen  and  their 
attachment  made  out  in  this  way  in  those  cases  where  there 
is  no  indusium  covering  the  sorus. 

{d)  ]\lake  a  vertical  section  through  a  sorus  and  stud}'  care- 
fully, looking  for  the  ring  of  darker  cells  on  the  spore  cases. 

(e)  Gametophytes  of  ferns  may  often  be  found  in  plant- 
houses  on  or  in  flower-pots  near  ferns.  They  may  be  obtained 
also  by  sowing  the  fresh  spores  in  flower-pots  and  keeping  them 
in  a  warm  damp  place  (a  greenhouse  is  best).  In  a  month  or 
two  the  gametophytes  will  be  full  grown.  Collect  a  few  of 
these  of  various  sizes,  carefully  wash  off  the  dirt  from  the  under 
side,  then  mount  in  water,  and  examine  the  untlcr  surface  for 


260  PHYLUM  IX.     PTERIDOPHYTA 

antherids  and  archegoncs.  By  careful  searching  j^oung 
fernlets  may  be  found  still  attached  to  the  gametophytes 
(prothallia). 

(/)  If  possible  secure  specimens  of  Adder-tongue,  and  com- 
pare the  structure  of  the  sporangia  with  the  foregoing. 

(g)  Search  the  borders  of  lakes,  ponds,  and  slow  streams  for 
Marsilias.  They  may  probably  be  found  in  every  part  of 
the  country,  although  they  are  rarely  collected. 

(h)  Where  possible  compare  the  structure  of  the  sporangia 
and  sori  of  Marattias  (from  greenhouses)  with  those  of  common 
ferns. 

(i)  In  some  places  it  is  possible  to  secure  sporophytes  of 
Isoetes  for  a  comparative  study. 

0")  Try  to  secure  fresh  spores  of  Isoetes  or  Marsilia  for  a 
study  of  heterospores,  and  of  the  antheridial,  and  archegonial 
gametophytes. 

LITERATURE  OF  PTERIDOPHYTA 

D.  H.  Campbell,  The  Structure  and  Development  of  Mosses  and 

Ferns,  New  York,  1905. 
N.  L.  Britton  and  Addison  Brown,  Illustrated  Flora  of  the 

Northern  States  and  Canada,  Second  Edition,  New  York, 

1913. 
B.  L.  Robinson  and  M.  L.  Fernald,  Graifs  New  Manual  of 

Botany,  New  York,  1908. 
J.  K.  Small,  Flora  of  the  Southeastern  United  States,  Second 

Edition,  New  York,  1913. 
L.  M.  Underwood,  Ferns  and  Fern  Allies,  New  York,  1905. 


CHAPTER  XVI 

PHYLUM  X.  CALAMOPHYTA 
THE  CALAMITES 

463.  As  far  as  we  know  them  the  Calamites  are  green 
plants  in  which  the  marked  difference  between  the  small 
gametophytes  and  the  large  sporophytes  seen  in  the 
Ferns  is  continued,  but  here  the  sporophyte  stems  are 
mostly  hollow  and  jointed,  and  the  leaves  relatively 
small.  A  great  difficulty  in  studjdng  the  plants  of  this 
phylum  is  that  although  common  in  the  Paleozoic 
period,  but  few  (about  24  species)  have  survived  to  the 
present  time,  and  our  knowledge  of  them  is  confined  to 
what  w^e  have  been  able  to  make  out  from  fragmentary 
fossils,  helped  out  in  some  details  by  a  study  of  the 
surviving  species. 

464.  This  much,  how^ever,  has  been  made  out  pretty 
certainly:  Gametophytes  small,  and  short-lived,  mostly 
monoecious;  Sporophytes  large,  long-lived,  with  roots, 
and  elongated,  cylindrical,  jointed,  often  hollow  stems, 
bearing  relatively  small  whorled  leaves  at  the  joints; 
spores  alike  (isospores),  or  of  two  kinds  (heterospores), 
borne  in  cones  of  sporophylls  (i.e.  special  spore-bearing 
leaves). 

465.  Like  the  Ferns  the  Calamites  have  well-developed 
tissues  in  the  sporophyte  generation;  the  vascular 
bundles  are  of  a  higher  type  ("collateral"),  and  are 
arranged  in  a  cylinder  in  the  stem.  When  these  bundles 
are  "open"  the  stems  have  the  power  of  increasing  in 

261 


262  PHYLUM  X.     CALAMOPHYTA 

diameter.     The  epidermis  is  abundantly  supplied  with 
stomata. 

466.  The  Wedge-leaved  Calamites  (Class  Spheno- 
phyllineae)  were  Paleozoic  herbaceous 
plants  of  moderate  dimensions,  whose  sporo- 
phyte  stems  Avere  solid,  jointed,  grooved  ex- 
ternally, and  at  the  joints  bore  spreading 
whorls  of  wedge-shaped  leaves.  Their  iso- 
spores  were  borne  in  terminal  cones  com- 
posed of  whorls  of  1-  or  2-sporangiate  spor- 

ophylls.     Sphenophyllum  is  the  typical  genus. 

467.  In  the  Horsetails  (Class  Equisetineae;  of  the 
present,  the  plant-body  of  the  sporophyte 
consists  of  a  hollow,  elongated  and  jointed 
herbaceous  stem,  bearing  whorls  of  narrow, 
united  leaves,  which  form  close  sheaths;  the 
stem  is  grooved,  and  is  usually  rough  and 
hard  from  the  large  amount  of  silica  depos- 
ited in  the  epidermis. 

468.  The  branches,  w^hen  present,  are  in 
whorls.  Both  the  main  axis  and  the  branches  are  in 
most  cases  richly  supplied  with  chlorophyll-bearing  tis- 
sue; but  in  some  of  the  species  the  stems  which  bear 
the  spores  are  destitute  of  chlorophyll.  All  of  the 
species  have  underground  stems,  which  bear  roots  and 
rudimentary  sheaths,  and  which  each  year  send  up  the 
vegetating  and  spore-bearing  stems. 

469.  The  Horsetails  are  perennial  plants.  In  some 
species  the  underground  portions,  only,  persist,  the 
aerial  stems  dying  at  the  end  of  each  year;  these  are  called 
the  annual-stemmed  species.  In  other  species  the 
aerial  stems  persist;  they  are  hence  known  as  perennial- 
stemmed. 

470.  The    epidermal    cells    are    mostly    narrow    and 


HORSETAILS  263 

elongated.  The  stomata  which  are  present  in  all  the 
chlorophyll-bearing  parts  of  the  plant,  are  arranged  with 
more  or  less  regularity  in  longitudinal  rows;  on  the  stem 
they  occur  in  the  channels  between  the  numerous  ridges. 
The  vascular  bundles  of  the  stem  are  disposed  in  a  cyl- 
inder and  run  parallel  with  each  other  from  node  to 
node,  where  they  join  with  one  another.  They  contain 
tracheary,  sieve  and  fibrous  tissues,  arranged  somewhat 
as  they  are  in  the  bundles  of  flowering  plants. 

471.  The  spores  of  Horsetails  are  produced  in  cones  at 
the  summit  of  the  stems.  The  cones  are  composed  of 
crowded  whorls  of  shield-shaped  leaves  (sporophylls), 
each  of  which  bears  upon  its  under  surface  five  to  ten 
sporangia.  The  spores  are  spherical,  and  at  maturity 
the  outer  wall  spUts  spirally  into  four  narrow  filaments 
{elaters)  which  unroll  when  dry,  and  roll  up  around  the 
spore  again  when  moistened.  Their  office  seems  to  be 
to  aid  in  setting  the  spores  free  from  the  spore-cases.  The 
spores  germinate  soon  after  falling 
upon  water  or  moist  earth,  enlarg- 
ing and  successively  dividing  until 
a  fiattish  irregular  gametophj'te 
(the  prothallium)  a  few  milli- 
meters in  l)readth  is  produced.  It 
bears  antherids  and  archegones  ^Jj--  JS'-'/S'SyTo,). 
resembling  those  of  the  ferns  upon 

its  lobes  or  their  edges;  in  some  cases  both  sexual  organs 
are  on  the  same  gametophyte,  while  very  commonly 
they  are  upon  separate  gametophytes,  although  the 
spores  show  no  differences.  The  sperms  are  spiral  and 
multiciliated. 

472.  This  class  contains  but  one  family  (Kquisc- 
taceae),  including  a  single  genus,' Eciuisetum.  and  twenty- 
four  species  of  herbaceous  plants  usually  a  meter  or  less 


264  PHYLUM  X.     CALAMOPHYTA 

in  height,  but  in  certain  tropical  species  attaining  a 
length  of  10  meters  or  more.  Among  the  better  known 
are  the  Common  Horsetail  {Equisetiim  arvense),  which 
sends  up  short  lived,  pale  or  brownish  cone-bearing  stems 
in  spring,  and  profusely  branching  green  stems  in  sum- 
mer {E.  telmateia,  the  Great  Horsetail  of  Europe  and  our 
own  Northwestern  region,  resembles,  but  is  larger  than, 
the  Common  Horsetail);  the  Woodland  Horsetail  {E. 
sijlvaticum),  whose  green  cone-bearing  stems  branch 
profusely  after  fruiting,  and  persist  all  summer;  and  the 
Scouring-rush,  called  also  Dutch  Rush  {E.  hiemale), 
with  green,  branchless  stems  which  produce  cones,  and 
survive  the  winter.  The  genus  Equisetum  originated  in 
the  Paleozoic  period,  and  so  is  ver}^  old.  Some  of  its 
species  have  become  extinct,  as  is  the  case  with  several 
related  genera. 

473.  The  Old  Calamites  (Class  Calamarineae)  were 
Paleozoic  plants  whose  sporophytes  were 
often  trees,  with  hollow,  jointed  stems, 
whose  collateral  vascular  bundles  allowed 
an  increase  in  diameter  by  the  develop- 
ment of  a  cambial  zone.  The  leaves 
were  separate,  narrow,  and  whorled  at 
op^'yte^anifspo^ea  the  joiuts  of  the  stcm.  The  heterospores 
of  Old  Caianute.  ^^^^^  bome  in  terminal  cones  composed 
of  whorls  of  sporophylls,  each  bearing  one  or  more  spo- 
rangia. Only  fragmentary  fossils  of  these  plants  are 
known. 

Laboratory  Studies,  (a)  Collect  in  early  spring  a  number 
of  cone-bearing  stems  of  the  Common  Horsetail.  Note  the 
joints  (nodes),  bearing  whorls  of  united  flat  leaves,  and  the 
cone,  composed  of  whorls  of  shield-shaped  leaves  (sporophylls). 
Split  the  cone  and  stem  and  note  that  the  latter  is  hollow,  with 
closed  nodes. 

(6)  Carefully  dissect  put  a  single  sporophyll  from  the  cone, 


LABORATORY  STUDU-.S  265 


and  examine  it,  using  a  low  power.  Note  the  sac-shaped  spore 
cases  upon  the  under  side  of  the  leaf.  JMount  some  of  the  spores 
dry,  using  no  cover-glass,  and  examine  with  the  16  mm. 
objective.  Breathe  upon  the  spores  very  gently  to  moisten 
them,  and  notice  the  coiling  of  the  elatcrs;  observe  the  quick 
uncoiling  which  takes  place  upon  the  evaporation  of  the 
moisture. 

(c)  Sow  a  quantity  of  the  fresh  spores  upon  moist  earth  or 
porous  pottery,  covering  with  a  bell-jar  and  taking  every  pre- 
caution to  secure  constant  moisture.  The  spores  will  begin  to 
germinate  in  a  few  days,  when  studies  of  successive  stages  of 
growth  may  be  taken  up.  By  care  the  mature  gametophytes 
(prothallia)  may  be  grown,  and  the  antherids  and  archegones 
studied. 

{d)  ]\Iake  ver}^  thin  cross-sections  of  the  stem  of  the  Common 
Horsetail.  Note  the  position  of  the  vascular  bundles.  Now 
make  a  vertical  section  of  the  bundles  and  study  the  tissues, 
using  high  powers. 

(e)  Study  the  breathing-pores  on  the  green  stems  of  the  Com- 
mon Horsetail.  Compare  these  with  those  of  the  Scouring 
Rush.  Study  also  the  disposition  of  the  chlorophyll-bearing 
tissue  in  cross-sections  of  both  stems. 

(/)  Examine  underground  stems  of  Horsetails,  and  compare 
the  structure  with  that  of  the  aerial  stems.  Make  cross-sec- 
tions of  the  roots  which  are  attached  to  these  underground 
stems. 

LITERATURE  OF  C.ALAMOPHYTA 

The  same  as  for  the  preceding  jihylum,  and 
M.  C.  Stopes,  Ancient  Plants,  London,  1910. 


CHAPTER  XVII 

PHYLUM  XL     LEPIDOPHYTA 
THE  LYCOPODS 

474.  Here  as  in  the  Calamites  we  are  dealing  with  a 
phylum  from  which  many  of  the  forms  have  disappeared 
through  extinction,  leaving  only  their  fragmentary 
fossils.  Yet  here  again  by  a  study  of  the  plants  that 
have  survived,  and  a  comparison  of  their  structure 
with  such  fossil  remains  as  have  been  found,  we  may  make 
out  pretty  clearly  the  nature  of  the  plants  that  constitute 
this  phylum. 

475.  Accordingly  the  Lycopods  may  be  characterized 
as  chlorophyll-green,  terrestrial  plants,  exhibiting  two 
generations  in  each  hfe-cycle,  viz. :  (1)  thegametophyte, 
which  is  small,  short-lived,  and  typically  tuberous  or 
globose,  with  few  rhizoids  or  none,  and  often  dioecious; 
the  sexual  organs  are  deeply  sunken,  and  the  sperms 
are  biciliated;  (2)  the  sporophyte,  which  is  large  and 
long-lived,  with  roots,  a  solid,  continuous  (not  jointed) 
stem,  and  many  small  spirally  arranged  or  opposite 
leaves,  some  of  which,  the  sporophylls,  with  sporangia 
in  their  axils,  are  in  terminal  cones.  The  spores  are 
mostly  heterosporous.  The  tissues  of  Lycopods  re- 
semble those  of  Ferns  and  Calamites  in  both  number 
and  kind.  Their  vascular  bundles  are  essentially  Uke 
those  of  the  Ferns  (concentric),  and  in  some  cases  are 
separate,  while  in  others  they  are  consolidated  into  a 
central  compound  bundle,  surrounded  by  a  mass  of  thick- 

266 


GROUND  PINES 


267 


walled    fibrous    tissue.     The    epidermis    is    abundantly 
supplied  with  stomata. 

476.  The  phylum  contains  about  700  living  species, 
and  consists  of  two  quite  distinct  classes,  viz.:  The 
Lower  Lycopods  (Class  Lycopodineae)  mainly  dis- 
tinguished by  being  isosporous,  and  the  Higher  Lycopods 
(Class  Lepidodendrineae)  which  are  heterosporous. 

477.  In  the  first  we  find  the  Ground  Pines  (Family 
Lycopodiaccae),  otherwise  known  as  Club-mosses,  which 
are  terrestrial,  perennial,  evergreen  plants  with  many 
small,  generally  moss-like  leaves  cover- 
ing the  stems.  The  sporophylls  are 
often  crowded  toward  the  summits  of 
certain  branches,  in  some  cases  form- 
ing well-marked  cones  (strobili).  The 
spores  are  all  of  one  kind,  and  are 
borne  in  roundish  sporangia  of  which 
there  is  one  on  the  upper  surface  of  sperms,  archegon 
each  leaf  near  the  base. 

The  Ground  Pines  are  common  in  the  Appa- 
lachian region,  Canada,  and  northwestward,  and  all 
belong  to  the  genus  Lycopodium,  including  L.  clavatum, 
L.  complanatum  and  L.  dendroideimi,  all  ex- 
tensively used  in  Christmas  decorations.  Fos- 
sil specimens  of  Ground  Pines  from  the  Paleo- 
zoic period  have  been  recorded. 

478.  In  the  second  class  are  the  Club-mosses 
(Family  Sclaginellaceae)  which  resemble  the 
Ground  Pines,  but  in  our  common  species  are 
generally  smaller  and  more  moss-like,  and 
have  (with  few  exceptions)  four-ranked  leaves. 
Their  sporangia  occur  singly  on  the  sporophylls 
which  are  clustered  into  terminal  spikes  (cones).  The 
spores  arc  of  two  kinds:  the  small   ones    (microspores) 


Fig.  141. — Lycopodium 
(gainetophyte,  antherid.s, 
ea   and 


©qo 


Fig.  142.— 
Lycopodium 
(sporophyte, 

sp  o  r  a  n  gia, 

Bpores). 


268  PHYLU:\I  XI.    LEPIDOPHYTA 

which  are  very  numerous  in  their  sporangia,  and  the 
hu'gcr  ones  (megaspores)  which  are  mostly  four  in  each 
sporangium.  These  microsporangia  and  megasporangia 
are  intermingled  in  the  cones.  When  mature  the 
microspores  fall  out  and  are  blown  awa}^,  but  it  often 
happens  that  the  megaspores  remain  in  the  old  wall  of 
the  megasporangium. 

479.  The  gametophytes  of  the  Club-mosses  have  almost 
disappeared.  When  a  microspore  germi- 
nates, it  becomes  divided  into  a  consider- 
able number  of  cells,  one  of  which  is  the 
remnant  of  the  gametophyte  (prothallium), 
while  the  other  cells  form  one  large  an- 
lagineiia   (game-    thcrid,   each   iuncr  cell  of  which  produces 

tophytes,    anthe-    ,  .    .,•     ,      i 

rid,     sperms,    ar-     blClliated  SpCrmS. 

c  egones,  egg  .  ^g^^  ^^^^  mcgaspore  likewise  produces  a 

very  small  but  many-celled  gametophyte,  which  pro- 
trudes but  little  from  the  ruptured  spore-wall.  Upon 
this  several  archegones  develop.  This  development 
may  take  place  while  the  megaspore  is  still  enclosed 
in  the  wall  of  its  sporangium.  After  fertilization  the 
egg  gives  rise  directly  to  a  leafy 
plant,  which  emerges  from  the  spore- 
wall  in  a  way  to  remind  one  very 
forcibly  of  the  growth  of  a  plantlet 
from  a  seed.  This  resemblance  is 
made  greater  by  the  hkeness  of  the  ^^^  i  4 4._seiagineUa 
first  leaves  to  cotyledons.  spo^esf ^^^^'  ^  ^  °  ^  ^  "  ^  '*• 

481.  But   one    genus,  Selaginella, 
is    known    in    this  family.     It   contains  many  species, 
most  of  which  are  tropical.     Several  species  are  com- 
mon throughout  the  United  States,  and  several  exotic 
species  are  frequently  cultivated  in  plant-houses. 


LEPIDODEXDRIDS  209 

482.  Allied  to  the  Club-mosses  are  the  arborescent 
Lepidodendrids  (Order  Lepidodendrales)  which  were 
abundant  in  the  Paleozoic  period,  and  which  disappeared 
in  the  Mesozoic.  We  have  fragmentary  fossils  of  the 
sporophytes,  which  were  large  dichotomously  branched 
trees,  sometimes  30  meters  high  and  a 

meter  in  diameter.     There  was  a  large    ^^&^^ 
central  vascular  bundle,  which   how-  V^  >t  1^ 
ever    formed   a    peripheral   cambium 
so  that  the  stems  increased  their  di- 
ameter much  as  in  the  case  of  higher 
plants.     The     stems     and    branches 
were    thickly    clothed    with    pointed  tZ^TolX'''"'  '''''" 
leaves  a  decimeter  or  more  in  length, 
and  when  these  fell  off  they  left  large  scars  of  charac- 
teristic shape  and  arrangement. 

483.  The  fossil  remains  of  the  spore-bearing  cones,  of 
which  many  specimens  have  been  found,  indicate  that 
they  contained  two  kinds  of  spores.  Hence  it  is  certain 
that  the  Lepidodendrids  were  allied  to  the  Club-mosses. 
The  more  common  genera  are  Lepidodendron,  and 
Sigillaria. 

Laboratory  Studies,  (a)  Secure  a  few  fresh  or  alcoholic 
specimens  of  various  kinds  of  Lycopods  in  fruit.  Ground 
Pines  may  be  collected  in  many  places  in  the  eastern  United 
States.     The  Club-mosses  may  be  obtained  in  plant-houses. 

(6)  IVIake  cross-sections  of  the  stems,  and  study  the  vascular 
bundles  in  Lycopodium  where  they  are  imbedded  in  a  thick 
mass  of  fibrous  tissue.  Examine  the  leaves,  noting  the  small 
vascular  bundle  in  the  midrib.  Stud}'  the  epidermis,  which 
contains  numerous  breathing-pores. 

(c)  In  like  manner  study  Selaginella. 

(d)  Carefully  remove  a  sporophyll  from  a  cone  of  Lycopo- 
dium, and  study  the  sporangium  and  spores.  Further  exami- 
nation will  show  that  the  spores  are  of  one  kind  only. 


270  PHYLUM  XI.    LEPIDOPHYTA 

(e)  Carefully  dissect  out  from  the  fruiting  cone  of  Selaginella 
several  sporangia,  some  with  four  large  spores,  and  others  with 
many  small  spores. 

LITERATURE  OF  LEPIDOPHYTA 

The  same  as  for  the  Ferns  and  Calamites. 


CHAPTER  XVIII 

PHYLUM  XII.     CYCADOPHYTA 

THE  CYCADS 

484.  Like  the  two  preceding  phyla  this  one  is  a  mere 
remnant  of  a  much  larger  group.  All  told  there  are  only 
about  140  living  species  belonging  to  six  families,  while 
we  know  of  as  many  more  families  whose  species  have 
become  extinct.  Enough  has  been  made  out  as  to  the 
structure  of  living  and  extinct  forms  to  enable  us  to 
define  the  Cycad  phylum  as  follows: 

485.  Their  archegonial  gametophytes  are  so  dependent 
that  they  are  enclosed  in  the  megaspore,  which  is  itself 
retained  in  the  sporangium;  the  antheridial  gametophyte 
is  minute  and  free,  and  its  tubular  antherid  typically 
develops  two  or  more  multiciliated  sperms;  after  fer- 
tilization of  the  egg  the  megasporangium  becomes  a 
''seed."  The  sporophyte  is  first  enclosed  in  the  seed, 
where  it  is  nourished  by  the  gametophyte,  and  later  it 
escapes  by  developing  roots  below,  and  expanding  its 
leaves  above;  eventually  some  leaves  become  sporophylls 
and  develop  microspores  and  megaspores. 

486.  It  is  instructive  here  to  compare  the  higher 
Lycopods  with  the  Cycads.  In  both  there  are  micro- 
spores and  megaspores,  and  in  both  the  microspores 
always  are  set  free  from  the  sporangium.  In  both  again 
the  microspore  produces  a  very  small  (one-  to  few-celled) 
gametophyte.  However,  the  antherid  of  the  higher 
Lycopods  is  a  few-celled  structure,  with  many  minute, 
biciliated  sperms,  while  in  the  Cycads  the  antherid   is 

271 


272  PHYLUM  XII.     CYCADOPHYTA 

reduced  to  a  simple  tube,  which  contains  usually  two 
large,  multiciliated  sperms  (suggesting  a  correlation 
between  size  and  the  number  of  sperms).  In  both 
phyla,  again,  the  megaspores  develop  from  a  spore 
mother-cell  (archespore)  as  tetrads,  but  while  in  the 
Lycopods  all  four  may  become  mature, 
in  the  Cycads  only  one  matures.  In  Ly- 
copods the  megaspores  separate  from  the 
sporangial  tissue  as  they  develop,  and 
normally  are  set  free,  while  in  Cycads 
Yia.  r46.— Cyoad  ^^®  smglc  mcgasporc  remains  perma- 
fnd  sSms!^^'  ^^^^  nently  connected  with  and  surrounded 
by  the  sporangial  tissue.  So  the  embryo 
sporophyte  of  the  former  normally  develops  outside  of 
the  megasporangium^  while  in  the  latter  it  does  so  in- 
side of  the  megasporangium,  and  thus  forms  the  seed. 

487.  The  lowest  Cycads,  the  so-called  **Seed-ferns" 
(Class  Pteridospermeae)  ,  were  abundant  in  the  Paleo- 
zoic period  and  are  now  known  only  from  their  fossil  frag- 
ments.    They  were  long   thought  to  be 

ferns  of  an  ancient  type,  but  are  now 

known  to  have  been  seed-bearing  plants. 

Apparently  they  were  derived  from  the 

Marattias  among  the  Old  Ferns.     Their 

leaves  were  fern-like  in  shape  and  struc-     fig.  147.— Pterido- 

ture.     Their  stems  were  capable  of  in-  and  seTd. '''°'°''^'^'' 

creasing  in  diameter.     It  is  now  thought 

that  the  Seed-ferns  constituted  a  group  of  vast  extent  in 

Paleozoic  times. 

488.  In  the  Common  Cycads  of  the  present  (Class 
Cycadineae)  the  sporophytcs  are  usually  erect,  woody, 
little-branched  trees,  rooted  below,  and  bearing  terminal 
crowns  of  evergreen,  pinnate  leaves.  The  collateral 
vascular  bundles  are  arranged  cylindrically  in  the  stem, 


COMMON  CYCADS  273 

and  increase  its  thickness  by  the  development  of  their 
cambium,  and  by  the  formation  of  new  bundles  in  the 
cortical  meristem.  The  sporophylls 
which  bear  microspores  and  megaspores 
form  more  or  less  distinct  cones  (strobili) 
but  occur  on  separate  plants  (dioecious). 

489.  The  common  greenhouse  Cycad 
(Cycas  rcvoluta)  produces  elongated, 
compact  cones  of  microsporophylls,  20  epoJophytt^' m^gT 
to  30  centimeters  long  and  5  to  6  centi-  c^osp^r^ophyiL"'^  ""' 
meters  thick.     Each  sporophyll  bears  on 

its  lowTr  surface  numerous  small  scattered  microspor- 
angia  containing  microspores,  constituting  the  so-called 
'^  pollen."  These  microspores  fall  out,  and  on  germi- 
nation produce  a  small  one-  or  two-celled  gametophyte, 
and  a  tubular  antherid  containing  tw^o  spirally  many- 
ciliated  sperms  (about  0.2  millimeter  in  diameter).  The 
megasporophylls  constitute  a  loose  terminal  cone  on  the 
main  axis  of  the  tree.  Each  sporophyll  bears  several 
laterally  placed  megasporangia  each  of  which  has  become 
covered  with  an  indusium-like  structure  (integument). 
Within  the  body  of  the  sporangium  (now  known  as  the 
ovule)  a  megaspore  develops,  l^ut  this  at  maturity  does 
not  fall  out  but  remains  surrounded  by  nutrient  tissue. 
Here  it  germinates  and  develops  a  solid,  many-celled 
spheroidal  gametophyte,  and  at  its  summit  forms  sev- 
eral deeply  sunken  archegones,  in  which  the  eggs  are  of 
remarkably  large  size  (2  to  3  millimeters). 

490.  Fertilization  of  the  egg  takes  place  as  follows: 
The  microspore  is  carried  by  the  wind  or  other  means  to 
the  opening  (micropyle)  at  the  summit  of  the  ovule 
integument;  there  it  germinates,  the  tubular  antherid 
penetrating  the  adjacent  tissues;  the  sperms  escape  by  the 
rupture  of  the  tube,  and  swim  through  the  intervening 

18 


274  PHYLUIM  XII.     CYCADOPHYTA 

watery  fluid  to  the  archegone,  finally  reaching  the  egg. 

From  the  fertilized  egg  there  is  later  developed  a  little 
sporophyte  which  is  nourished  for  a 
time  by  the  tissue  of  the  surrounding 
gametophyte.  In  the  meantime  the 
integument  of  the  sporangium  has 
greatly  thickened  into  a  mass  of  tissue 
Fio.     i49.-zanna  ^^^^    extcmally    and    stony   internally. 

to°h"'tcr''  """^  ^^"''''  ^^'^^^^'^  ^^^  growth  ceases  the  megaspor- 
angium    (ovule)     with    its     contained 

gametophyte  and  sporophyte  falls  off,  as  the  ''seed." 

491.  After  the  fall  of  the  seed  when  placed  in  proper 
conditions  as  to  moisture  and  temperature,  the  sporo- 
phyte resumes  its  growth  at  the  expense  of  the  game- 
tophyte (now  called  ''endosperm"),  and  soon  sends  out  a 
root,  and  later  a  green  leaf,  after  which  it  becomes  an 
independent  long-lived  plant. 

492.  The  other  living  Cycads  are  essentiall}^  similar 
in  structure  to  the  foregoing.  All  of  the  species  are 
tropical  or   subtropical.     jVIany  that 

lived   in   Mesozoic   times    have  long 
been  extinct. 

493.  In  the  Mesozoic  period  there 
flourished  a  group  of  Cycads  that  may 
be  called  the  "Flowering  Plant  An- 
cestors"    (Class    Bennettitineae),    ^''^-  ^?Pfl~^?M°^"^^'' 
and  which  had  "flowers"  containing 

a  central  cluster  of  stalked  megasporangia,  surrounded 
by  a  whorl  of  pinnate  microsporophylls.  Below  these 
were  many  sterile  bracts  reminding  one  of  flower-leaves 
(perianth).  The  resemblance  of  this  primitive  flower 
to  the  flowers  of  the  simpler  Flowering  Plants  such  as 
Magnolia,  Asimina,  Ranunculus,  etc.,  is  so  great  as  to 
suggest  a  genetic  relationship. 


CORDAITALES  AND  GIXKGOALES  275 

494.  The  Conifer  Ancestors  of  the  Paleozoic  period 
(Order  Cordaitales)  were  hirge  trees  30  or  more  meters 
in  height,  and  bearing  a  dense  crown  of  ])ranches  and 
hirge,  paraHel-veined  leaves,  sometimes  a  meter  or  so 
in  length.  Microspore  and  megaspore  cones  are  known, 
and  even  the  seeds  have  been  preserved,  and  many  of 
their  details  of  structure  made  out. 


Fig.   151. — Cordaites.  Fig.   152. — Ginkgo  (staniinate 

and  ovulate). 

495.  The  Maidenhair  Trees  (Order  Ginkgoales)  re- 
mind one  in  some  respects  of  the  preceding.  They  were 
common  in  the  Mesozoic  period,  but  all  are  now  extinct 
excepting  a  single  species  {Ginkgo  biloha)  from  eastern 
Asia.  They  have  parallel-veined,  fan-shaped  leaves, 
and  branching,  woody  stems.  In  the  surviving  species 
the  trees  are  dioecious.  The  bisporangiate  micro- 
sporophylls  constitute  a  loose  cone,  while  the  mega- 
sporophylls  remind  one  of  those  of  Cycas  described 
above.  The  seed  integument  becomes  fleshy  externally 
and  stony  internally  when  mature. 

496.  The  Joint-firs  (Order  Gnetales),  including  several 
rather  widely  separated  families,  should  probably  ])e 
placed  here,  although  their  relationship  is  doubtful, 
especially  since  they  have  non-ciliated  sperms.  Ephedra 
is  a  widely  distributed  genus  of  green,  branching,  leafless 
shrubs  resembling  Equisetum  in  appearance.  Gnetum 
includes  tropical  shrubs  and  trees  with  large  pinnately 
veined  leaves;  Tumboa  (Welwitschia)  occurs  in  tropical 
west  Africa. 


276  PHYLUM  XII.     CYCADOPHYTA 

Laboratory  Studies,  (a)  In  many  greenhouses  may  be 
found  well-grown  sj^ccimens  of  Cycas  and  Zamia.  Examine 
these  for  the  general  appearance  of  Cycads. 

(b)  On  inquiry  it  is  possible  that  microspore  cones  of  these 
common  Cycads  may  be  found,  and  secured  for  a  closer  study. 

(c)  Old  trees  of  Cycas  produce  their  '^ flowers"  of  mega- 
sporophylls  every  few  years,  and  on  inquiry  some  of  the  latter 
may  be  secured  in  various  stages  of  development  for  dissection 
and  study. 

(d)  Zamia  plants  in  greenhouses  frequently  produce  their 
thick,  rounded  megasporophyll  cones.  These  should  be  dis- 
sected to  find  the  sporangia  (seeds). 

(e)  It  should  be  remembered  that  various  Cycads,  including 
Cycas  and  Zamia,  grow  in  the  Gulf  states,  and  specimens  may  be 
obtained  for  study  without  much  difficulty. 

(/)  Ginkgo  trees  are  grown  in  many  parks  and  door  yards, 
and  may  be  examined  for  their  foliage  and  general  appearance. 

(g)  In  the  spring  look  for  microsporophylls  and  megasporo- 
phylls  of  Ginkgo  and  later  for  ripe,  fleshy  seeds. 

(h)  From  the  middle  of  June  to  early  in  July,  depending 
upon  the  location,  the  sperms  can  sometimes  be  observed  in  the 
seeds  as  follows:  Take  a  seed  and  with  a  stout  knife  split  off 
two  opposite  sides  (including  the  stony  part  of  the  integument). 
If  properly  made  a  slice  will  be  removed  from  each  side  of  the 
megagametophyte  which  can  be  removed  with  a  portion  of 
the  megasporangium  (nucellus)  adhering  as  a  cap  to  its  apex. 
Upon  carefully  lifting  this  cap  the  microgametophytes  will  be 
found  hanging  to  its  under  side  as  thick,  glistening,  tube-like 
bodies.  Carefully  dissect  these  off  with  very  sharp  scalpel 
and  mount  in  a  solution  containing  about  5  per  cent,  of  cane 
sugar.  The  sperms  (or  at  least  the  cells  from  which  they  arise) 
will  readily  be  visible  even  under  low  power  of  the  microscope, 
as  they  are  very  large,  attaining  a  diameter  of  0.1  millimeter. 


LITERATURE  OF  CYCADOPHYTA 

J.    M.    Coulter   and    C.    J.    Chamberlain,    Morphology   of 

Gymnosperms,  Chicago,  1910. 
M.  C.  Stopes,  Ancient  Plants,  London,  1910. 


CHAPTER  XIX 

PHYLUM  XIII.     STROBILOPHYTA 
THE  CONIFERS 

497.  To  a  large  extent  this  is  a  phylum  of  living  plants, 
and  although  many  species  and  some  genera  have  be- 
come extinct,  everj^  family  is  still  represented  in  some  part 
of  the  world.  The  number  of  living  species  is  about  400, 
widely  distributed  throughout  the  earth.  The  Conifers 
probably  were  derived  from  some  of  the  old  Cycads 
{Cordaitales)  to  which  they  show  some  affinities. 

498.  In  these  plants  there  is  a  still  more  marked 
alternation  of  generations  than  in  the  preceding  phyla. 
The  gametophytes  are  so  minute  and  short-lived  that 
they  are  rarely  seen,  while  the  sporophytes  are  mostly 
great  trees  with  long-lived  perennial  roots  and  stems  and 
mostly  perennial  green  leaves  also.  The  phylum  may  be 
defined  as  follows:  Megaspores  and  microspores  mostly 
borne  in  homogeneous  cones  of  sporophylls  on  the 
arboreous  sporophytes.  Archegonial  gametophytes  very 
minute,  solid,  ellipsoid,  and  permanent]}'  enclosed  in  the 
megaspore,  which  in  turn  is  retained  in  the  megasporan- 
gium;  antheridial  gametophyte  minute,  few-celled,  free, 
developing  a  tubular  antherid  containing  two  noncili- 
ated  sperms.  After  the  fertilization  of  the  egg  and  the 
formation  of  the  cylindrical,  leafy  sporophyte,  the 
megasporangium,  covered  by  an  indusial  coat  (integu- 
ment), becomes  a  ''seed."  The  sporophyte  upon  esca})ing 
from  the  seed  in  germination  grows  into  a  perennial, 

277 


278  PHYLUIM  XIII.    STROBILOPHYTA 

long-lived  tree,  rooted  below,  and  bearing  green  (mostly 
perennial)  leaves  above. 

499.  Since  the  sporophytes  are  large  and  long-lived 
their  tissues  are  many  and  well-developed.  Their 
tracheary  tissue  is  almost  wholly  of  the  form  known  as 
tracheids,  which  are  here  marked  on  their  radial  faces 
with  ])ordered  pits.  Proper  fibrous  tissue  is  scanty  or 
wanting.  The  vascular  bundles  are  of  the  open  collateral 
type,  arranged  in  a  cyUnder  so  that  they  provide  for 
increasing  the  diameter  of  the  stems  and  roots.  Turpen- 
tine canals  are  present  in  all  parts  of  the  plant. 

500.  There  are  nine  families  of  conifers,  a  few  only  of 
which  need  be  noticed  here.  In  all  the  microspore  cones 
are  well  developed,  but  there  is  a  gradual  simpUfication 
of  the  megaspore  cones  from  those  with  many  sporo- 
phylls  to  those  with  few  or  one.  The  Taxodiums  (Family 
Taxodiaceae) ,  Microsporophylls  with  two  to  eight  spor- 
angia: megasporophylls  woody,  much  en- 
larged distally,  bearing  two  to  several  erect 
or  inverted  seeds,  forming  compact,  elhpsoid 
cones;  ''seed  scale"   wanting.     Here  are  the 

Sequoia  (seed-  Bald  Cypresscs  (Taxodium)  and  Redwoods 
(Sequoia),  very  old  types  that  originated  in 
the  Mesozoic,  and  have  persisted  with  reduced  numbers 
to  the  present.  The  Redwoods,  now  confined  to  the 
mountains  of  California,  were  once  widely  distributed 
in  the  Northern  Hemisphere. 

501.  The  Old  Pines  (Family  Araucariaceae) .     Micro- 
sporophylls   with    five    to    fifteen    spor-  j, 
angia:  megasporophylls   woody,    slightly     /^^  ^m 
enlarged   distally,    bearing    one    inverted    *             ^P 
seed,  forming  compact  spheroidal   cones;  Fig.  154— Arauca- 
"seed    scale"     rudimentary.      The    Old 

Pines  are  now  confined  to  the  Southern  Hemisphere,  and 


PINES  279 

are  represented  by  but  two  living  genera,  Araucaria  and 
Agatliis.  These  and  other  genera  were  represented  in 
the  Northern  Hemisphere  in  Mesozoic  and  later  periods. 

502.  Modern  Pines  (Family  Ahietaceae).  These  may 
be  illustrated  by  the  common  Scotch  Pine  {Pinus  silves- 
iris),  in  which  the  microsporophylls  are 
massed  into  cones  1  centimeter  long,  and 
these  cones  are  themselves  massed  in  clus- 
ters. Each  microsporophyll  bears  two  spor- 
angia on  its  lower  surface.  The  microspores 
are  spheroidal  but  the  outer  layer  of  the  p^^^^ 
wall  is  often  swelled  out  into  two  bladder-  spore  cone  and 

microspore). 

like    distentions    at   opposite   sides.     These 
microspores   C' pollen")    escape   from   the  sporangia   in 
the  spring,  and  may  be  carried  by  the  wind  for  long 
distances  (sometimes  for  hundreds  of  miles). 

503.  The  megaspore  cones  grow  singly  near  the  ends 
of  the  upper  twigs  of  the  season's  growth,  and  are  about 

1  centimeter  long.  They  consist  of  an 
axis  on  which  are  borne  flat  megasporo- 
phylls,  each  bearing  two  inverted  mega- 
sporangia  (ovules).  In  these  plants  fertili- 
zation is  a  slow  process:  the  microspores 
Fig.  156.— Pinus  Carried  by  the  wind  fall  between  the  meg- 
see  -cone).  asporophylls  (in  the  spring  or  early  sum- 
mer), where  each  spore  pushes  out  a  tubular  antherid 
("pollen  tube")  which  penetrates  the  ovule  tissue.  This 
stimulates  the  growth  of  the  tissues  of  the  cone  and  it 
increases  in  size  and  bends  downward  on  its  stalk.  In 
the  meantime  the  ovules  enlarge,  the  upper  ("chalazal") 
end  doveloi)ing  a  thickened  mass  of  grcMMi  tissue  which 
grows  far  beyond  the  end  of  the  sporojihyll,  constituting 
the   ''seed   scale."     These   green   "seed   scales''  are  in 


280  PHYLUM  XIII.    STROBILOPHYTA 

reality  the  distal  portions  of  the  ovules,  and  function  as 
photosynthetic  structures  for  a  year  (or  more). 

504.  In  the  first  summer  or  autumn  an  axial  spore 
mother-cell  C'archespore")  arises  in  the  interior  tissues 
of  the  ovule,  and  this  ultimately  divides  into  four  cells 
(four  young  megaspores),  only  the  lowermost  of  which 
enlarges  into  the  fully  developed  megaspore.  By  the 
second  spring  this  megaspore  has  divided  and  subdivided 

until  a  solid  ellipsoidal  cellular 
mass  is  formed — the  gameto- 
phyte.  Then  from  certain  cells 
on  the  summit  of  the  gameto- 
phyte  several  (usually  four) 
sunken  archegones  arise,  when 
Fig    157— Pinus  (archegoniai,   everything  is  ready  for  the  com- 

andanthendial  gametophytcs).  ^  o  ^ 

pletion  of  the  process  of  fertili- 
zation. In  the  meantime,  the  pollen  tube  resumes  its 
growth,  bringing  the  two  non-ciliated  sperms  to  the 
mouth  of  an  archegone  where  one  of  the  sperms  soon 
fuses  with  the  egg,  and  fertilization  is  completed,  a 
little  more  than  a  year  after  pollination. 

505.  By  repeated  subdivision  and  continued  growth 
of  the  zygote  a  cylindrical  stem  is  formed,  rooted  below, 
and  with  a  whorl  of  narrow  leaves  above.  This  is  the 
sporophyte  (or  "embryo"  of  the  seed).  It  is  nourished 
by  the  gametophyte  tissue  in  which  it  is  imbedded.  In  the 
meantime  ovule,  "seed  scale,"  and  cone  have  increased 
in  size,  and  later  the  "seed  scales"  lose  their  chlorophyll 
and  become  woody.  Still  later  by  the  lessened  supply 
of  water  all  parts  of  the  cone  become  dry,  stopping  the 
growth  of  the  young  sporophyte.  The  cone-  and  seeds 
are  now  "ripe,"  and  by  the  spreading  of  the  dry  scales 
the  part  of  the  seed  containing  the  embryo  is  split  loose 
and  blown  away. 


Pinus  (seeds,  and 
young  sporo- 


PINES  281 

506.  Germination  of  the  seed  takes  place  when  water 
is  again  suppUecl,  resulting  in  a  resumption  of  the  growth 
of  the  embryo,  the  bursting  of  the  brittle 
integument  (indusium)  and  the   escape  of  nN\\|/A 
the  root,  stem   and  leaves  of  the  embryo.    C^^^f^ 
The  root  penetrates  the  soil  and  provides    C^^\  \  i 
water,  while   the   leaves   (now  green)  pro-     . — ^   ( 
vide  carbohj^drates,  completing  the  estab- 
lishment of  the  new  plant.                                   f  i  a .  1 5  s 

507.  There  are  about  half  a  dozen  genera 
of    Modern    Pines,   distinguished  by  their  ^^^^""^^ 
leaves  and  cones,  as  follows: 

I.  Twigs  with  primary  green 
leaves  only. 

1.  Cone  scales  persistent. 

i.  Leaves  prismatic,   four- 
angled.  (Spruces)      Picea 
ii.  Leaves  fiat. 

(a)  Megasporophylls  (False 

long,  protruding.  Hemlocks)  Pseudotsuga 

(6)  Megasporophylls 
short,  not  protrud- 
ing. (Hemlocks)  Tsuga 

2.  Cone  scales  deciduous,  the 

cone  falling  to  pieces.  (Firs)  Abies 

H.  Twigs  with  both  primary  and 
secondary  green  leaves. 
L  Leaves  evergreen.  (Cedars)        Cedrus 

2.  Leaves  deciduous.  (Larches)       Larix 

in.  Twigs    with  only  secondary 

green  leaves.  (Pines)  Pinus 

508.  The  very  young  twigs  of  the  last  genus  (Pinus)  are 
covered  with  flat  primary  leaves  which  die  immediately, 
and  in  their  axils  short  twiglets  push  out  bearing  five, 
three  or  two  very  narrow  leaves,  the  secondary  leaves, 
which  are  the  only  ones  persistent  on  these  plants.     Com- 


282  PHYLUM  XIII.     STROBILOPHYTA 

mon  ''White  Pines"  have  five  leaves  in  a  fascicle,  the 
"Yellow  Pines"  three  or  two.  An  Arizona  pine  has  but 
one  leaf  on  each  twiglet. 

509.  In  the  Cypresses  (Family  Ciipressaceae),  and 
Thuyas  (Family  Thuyopsidaccac)  the  woody  cones  are 
small  and  composed  of  only  a  few  scales,  and  the  leaves 
are  small  and  scale-like.  In  the  Junipers  (Family  Juni- 
peraceac)  some  twigs  bear  scale-leaves  and  others  fiat 
leaves,  while  the  cone  scales  are  few  and  fleshy,  so  that 
the  cones  are  fleshy.  In  the  Yews  (Order  Taxales)  the 
reduction  in  the  cones  is  carried  so  far  that  but  one  scale 
remains,  and  that  has  become  fleshy.  In  the  proper 
Yews  (Taxus)  the  leaves  are  flat,  but  in  some  related 
genera  they  are  scale-like. 

Laboratory  Studies,  (a)  In  the  spring  of  the  j^ear  collect  a 
quantity  of  the  microspore  (staminate)  cones  of  a  pine  (Scotch 
or  Austrian  are  very  good),  and  preserve  such  as  are  not  wanted 
for  immediate  use  in  alcohol.  Collect  at  the  same  time  the 
3'oung  megaspore  (ovule-bearing)  cones  which  are  to  be  found 
at  the  ends  of  the  new  shoots. 

(6)  SpUt  both  kinds  of  cones  vertically,  and  study  their 
structure,  comparing  the  one  with  the  other. 

(c)  Study  microspores  from  young  and  mature  cones.  In 
the  young  microspores  look  for  the  cells  representing  the  game- 
tophyte;  in  the  mature  microspores  note  the  bladder-like 
enlargements  of  the  outer  coat. 

((/)  Study  young  megaspore  cones  of  different  ages,  and  note 
the  growth  of  the  "seed  scale." 

(e)  Study  megaspore  cones  one  year  old  and  note  the  devel- 
opment of  the  gametophyte,  and  later  the  archegones. 

(/)  Note  that  the  megaspore  cones  of  Scotch  and  Austrian 
pines  are  two  years  in  coming  to  maturity.  Make  vertical 
sections  of  cones  of  various  ages,  and  note  the  growth  of  the 
seed.  Note  the  thin  wing  (useful  in  their  dispersion)  on  the 
seeds.  Make  longitudinal  sections  of  seeds,  and  note  the 
little  sporophyte  with  its  several  leaves  (cotyledons). 

(g)  Examine  the  very  young  twigs  as  they  develop  in  the 


LABORATORY  STUDIES  283 

spring  and  note  the  primary  leaves  with  the  growth  of  twiglets 
in  tlieir  axils  bearing  young  secondary  leaves. 

(h)  Make  cross-sections  of  mature  leaves,  and  note  the 
turpentine-canals,  one  near  each  angle,  with  others  symmetric- 
ally arranged  between.  JMake  cross-sections  of  the  young 
twigs,  and  note  the  canals  in  the  rind  or  bark.  Make  similar 
sections  of  the  wood  of  the  trunk,  and  note  similar  canals  at 
intervals. 

(0  Make  very  thin  cross-sections  of  the  mature  wood  of  the 
stem  and  note  shape  and  size  of  the  cells;  note  also  the  gradual 
decrease  in  their  size  in  passing  from  the  inner  to  the  outer  side 
of  a  growth  ring.  Now  make  a  very  thin  longitudinal-radial 
section,  and  observe  the  bordered  pits.  A  longitudinal  section 
at  right  angles  to  the  last  (longitudinal-tangential)  will  show 
no  bordered  pits.  In  all  these  sections  note  that  the  wood  is 
made  up  of  but  one  kind  of  cells,  viz.  tracheids. 

(j)  In  a  cross-section  of  a  stem  note  the  thin  radiating  plates 
of  tissue  (medullary  rays),  in  many  cases  extending  from  pith 
to  bark.  In  longitudinal-tangential  section  of  the  stem  these 
rays  are  seen  in  cross-section  to  be  made  of  thick-walled  cells. 
In  longitudinal-radial  sections  the  raj^s  are  seen  split  lengthwise. 

(k)  Make  very  thin  cross-sections  of  the  stem  through  bark 
and  wood,  and  note  the  layers  of  ver}^  soft  thin-walled  tissue 
(cambium)  between  wood  and  bark.  This  may  be  made  more 
evident  bj'  soaking  the  section  for  some  time  in  eosin,  by  which 
the  cambium  will  be  stained. 

(l)  Compare  the  cones  of  Pinus,  Picea,  Abies,  Taxodium, 
Sequoia,  Cupressus,  Thuya,  and  Juniperus. 

(7/1)  Compare  the  leaves  of  Pinus,  Picea,  Abies,  Thuya,  and 
Juniperus. 

LITERATURE  OF  STROBILOPHYTA. 

J.    AI.    Coulter    and    C.    J.    Chamberlain,    Morphology    of 

Gijmnoa perms,  Chicago,  1910. 
C.   S.  Sargent,  Manual  of  the  Forest  Trees  of  Xorth  Amei'ica, 

Boston,  1905. 


CHAPTER  XX 

PHYLUM  XIV.     ANTHOPHYTA 

FLOWERING  PLANTS 

510.  In  this  highest  phylum  we  have  the  culmination 
of  the  repeated  structural  advances  in  earlier  phyla. 
These  plants  are  mainly  modern,  although  some  of  the 
more  primitive  forms  originated  as  far  back  as  the 
Cretaceous  period.  It  includes  more  than  132,000  known 
species,  that  is,  more  than  all  the  other  phjda  together. 

511.  The  Anthophyta  probably  were  derived  from  the 
Bennettitales  among  the  Cycads.  It  is  certain,  at 
any  rate,  that  the  flower  structure  of  this  ancient  order 
bears  a  remarkable  resemblance  to  that  of  the  lower  orders 
of  the  Flowering  Plants. 

512.  This  phylum  may  be  characterized  summarily  as 
follows:  Microspores  and  megaspores  borne  in  flowers 
on  the  leafy,  rooted  sporophytes.  Flowers  normally 
consisting  of  more  or  less  cone-like  clusters  of  closed 
megasporophylls  (carpels)  above,  and  microsporophylls 
(stamens)  below,  and  subtended  by  a  perianth.  Micro- 
spores (pollen-cells)  free  at  maturity,  each  producing  a 
one-celled  gametophyte,  and  a  tubular  antherid,  the 
latter  containing  two  non-ciliated  sperms.  Megaspore 
retained  within  the  megasporangium  (ovule)  where  it 
develops  an  egg  in  a  reduced  archegone  and  imma- 
ture gametophyte.  After  fertilization  the  gametophyte 
matures  ("endosperm"),  and  the  zygote  develops  into 
a  cylindrical,  leafy  sporophyte.     The  megasporangium 

284 


THE  FLOWER  285 

(covered  by  one  or  two  indiisial  coats)  now  becomes  the 
*'seed."  Upon  germination  of  the  seed  the  sporophyte 
escapes,  sending  its  roots  downward  into  the  soil,  and 
its  stem  upward  into  the  light,  bearing  green  (annual 
or  perennial)  leaves. 

513.  The  tissues  of  the  Flowering  Plants  show  a  higher 
development  than  in  any  of  the  preceding  phyla. 
They  range,  in  size  and  duration,  from  herbs,  a  few 
millimeters  in  extent  and  living  but  a  few  days  or  weeks, 
to  enormous  trees,  50  to  100  meters  high  and  many 
centuries  old;  they  live  in  all  kinds  of  habitats  from  very 
wet  to  very  dry,  and  from  the  most  protected  to  the  most 
exposed  situations;  accordingly  their  tissues,  especially 
those  which  are  supporting  and  conducting,  show  all 
degrees  of  variation  from  very  simple  to  the  most  com- 
plex. The  supporting  and  conducting  bundles  are  here 
frequently  united  into  fibrovascular  bundles,  which  in  the 
higher  forms  remain  ^'open"  and  are  arranged  in  a  cyl- 
inder in  the  stem,  thus  providing  a  cambium  zone  for 
the  thickening  of  the  perennial  stem. 

514.  Most  Flowering  Plants  are  terrestrial  and  chloro- 
phyll-bearing; there  are,  however,  many  aquatic  and 
aerial  species,  and  a  considerable  number  of  parasites 
and  saproph^'tes. 

515.  A  Typical  Flower.  Flowers  have  so  many  par- 
ticular forms  that  it  would  be  impossible  to  describe 
them  here,  and  yet  they  all  conform  to  a  general  plan  of 
structure.  In  other  words,  each  particular  flower  shows 
a  greater  or  less  modification  of  or  departure  from  what 
may  be  called  the  typical  structure. 

516.  First  of  all,  every  flower  has  a  central  stem  por- 
tion (axis),  on  which  there  grow  pistils,  stamens,  and  a 
perianth.  This  flower  axis  may  ])e  elongated,  glo])u]ar 
or  very  short,  or  it  may  be  flattened  into  a  disk  or  hollow 


286  PHITUM  XIV.    ANTHOPHYTA 

cup    (''receptacular   cup")-     In   such   a  typical   flower 
as  a  Buttercup  (Ranunculus)  this  axis  is  globular. 

517.  In  the  Buttercup  the  globular  axis  is  spirally 
studded  with  many  carpels  (simple  pistils)  each  consisting 
of  a   closed   cavity   below   (ovar}'),   gradually  tapering 

above  to  the  soft  terminal  part  (stigma). 

When  young  the  carpel  (megasporophyll) 

is  an  open,  flattish,  leaf-like  structure,  but 
vert'i^ai  pian'^  as  it  grows  larger  its  margins  curve  up- 
flowrr"''"''^'''   ^vard  until  they  meet  and  grow  together. 

While  the  carpel  is  closing,  an  ovule  grows 
out  from  the  base,  and  becomes  enclosed  by  the  carpel 
walls. 

518.  Below  the  globular  head  of  carpels  (pistils)  are 
several  rows  of  stamens  spirally  encircling  the  axis.  Each 
stamen  is  a  stalked,  somewhat  flattish  structure  (micro- 
sporophyll),  bearing  four  elongated,  parallel  sporangia 
which  contain  microspores  (pollen).  Commonly  the 
stalk  is  called  the  filament,  and  the  four  sporangia  to- 
gether, the  anther.  The  sporangia  (pollen  sacs)  split 
longitudinally  at  maturity  and  permit  the  escape  of  the 
pollen. 

519.  Still  lower  on  the  flower  axis  are  two  series  of 
leaf-like  structures  also  spirally  arranged,  constituting 
the  perianth.  The  upper  series  includes  five  rounded, 
yellow  petals,  the  whole  being  known  as  the  corolla. 
The  lower  series  is  made  up  of  five  pointed,  green  sepals, 
this  being  known  as  the  calyx. 

520.  The  purpose  of  a  flower  is  the  production  of 
seed,  and  in  the  Buttercup  this  is  accomplished  as 
follows: 

521.  In  the  ovule  (megasporangium)  an  axial  spore 
mother  cell  (archespore)  arises,  and  later  this  divides 
into  four  young  cells  (megaspores),  but  only  the  deeper 


DEVELOPMENT  OF  THE  SEED 


28; 


lying  one  of  these  develops,  the  others  perishing.  So  the 
ovule  comes  to  have  one  megasporc,  which  is  retained  in 
the  ovule  tissues.  A  little  later  this  megaspore  develops 
an  egg  in  connection  with  a  greatly  reduced  archegone, 
and  a  very  immature  gametophyte,  in  the  following 
manner: 

The  nucleus  of  the  megaspore  divides  into  two,  which 
move  to  opposite  poles  of  the  megaspore  cavity;  here 
they  divide  twice  resulting  in  four  nuclei  at  each  pole; 
then  a  nucleus  from  each  pole  (the  so-called  polar  nuclei) 
moves  to  the  center,  where  they  ultimately  unite.  At 
the  upper  (micropylar)  end  one  of  the  (naked)  cells 
becomes  the  egg,  accompanied  by  two  companion  cells 


Fig.  160.— Ra- 
nunculus (pistil 
and  seed). 


Fig.   IGl. — Ranunculus  (dc- 
velopincnt  of  ovule). 


Fig.   1G2.— P( 
Icn, tubular  anthe- 
rid  and  sperms. 


C'synergids").  At  the  lower  end  are  the  antipotlal 
nuclei  (or  cells) .  About  this  time  any  pollen  cell  (micro- 
spore) that  may  have  fallen  upon  the  soft  tissue  of  the 
carpel  stigma  germinates  there  producing  its  most 
reduced  gametophyte,  and  a  tubular  antherid  (pollen 
tube).  The  latter  penetrates  the  soft  stigma  tissues 
toward  the  ovary  cavity,  carrying  down  the  two  sperms. 
When  the  tubular  antherid  reaches  the  ovule  it  enters 
the  little  pore  (micropyle)  at  the  summit  of  the  indusial 
coats,  and  penetrates  the  ovule  to  the  egg  where  one  of 
the  sperms  then  unites  with  the  egg,  this  constituting 
fertilization.     The  zygote  now  divides  repeatedly   and 


288  PHYLUM  XIV.    AXTIIOPHYTA 

finally  takes  the  form  of  a  verj^  small  stem,  tipped  with 
a  root  at  one  end,  and  bearing  two  rudimentary  leaves 
at  the  other.  In  the  meantime  the  immature  game- 
tophyte  resumes  its  development  as  the  result  of  the 
union  of  the  second  sperm  nucleus  with  the  two  polar 
nuclei  to  form  the  so-called  endosperm  nucleus,  which  by 
its  rapid  division,  with  much  delayed  formation  of  cell 
walls,  results  in  the  development  of  a  mass  of  tissue 
surrounding  and  nourishing  the  embryo  sporophyte 
and  filling  the  growing  ovule.  It  is  now  known  as  the 
endosperm,  but  it  is  in  reaUty  only  the  belated  game- 
tophyte. 

522.  The  ovule  has  now  grown  much  in  size.  Ex- 
ternally its  outer  coat  has  become  thicker  and  harder, 
•while  internally  the  gametophyte  has  enlarged  and  solidi- 
fied. A  layer  of  cells  at  the  base  of  the  ovule  now 
becomes  corky  and  checks  the  supply  of  water,  drjdng 
and  hardening  the  whole  ovule,  and  stopping  further 
growth.  In  this  final  state  the  ovule  is  called  the 
seed. 

523.  In  the  Buttercup  the  carpel  enlarges  to  accom- 
modate the  growing  ovule,  but  finally  its  tissues  harden 
and  dry  so  that  when  the  seed  is  mature  it  is  contained 
within  the  close-fitting  wall  of  the  old  carpel  and,  in  this 
condition,  it  finally  falls  off  from  the  flower  axis  and  is 
known  as  a  fruit.  The  term  "fruit,"  therefore,  is  here 
used  for  the  ripened  carpel  and  its  contained  seed,  and 
in  flowering  plants  this  is  the  generally  accepted  signi- 
fication of  the  term. 

524.  When  these  fruits  fall  to  the  ground  and  absorb 
moisture,  the  eml^ryo  plant  in  each  seed  renews  its 
growth,  getting  its  food  from  the  endosperm.  At 
length  it  is  able  to  push  out  a  root  into  the  soil,  and  much 
later  it  escapes  wholly  from  seed  and  fruit  and  pushes  up 


WATER  PLANTAIN  289 

its  stem  and  leaves  to  the  light  above  ground,  and  be- 
comes an  independent  plant  (sporophyte). 

525.  The  flower  structure  of  the  Water  Plantain 
(Alisma)  is  essentially  the  same  as  that  of  the  Buttercup. 
In  it  the  flower  axis  is  less  enlarged,  the  carpels  are 
fewer,  in  only  a  single  whorl  (i.e.  not  spirally  arranged), 
and  the  stamens  are  usually  six.  The  rounded,  white  petals 
are  in  a  whorl  of  three,  and  the  pointed,  green  sepals  are 
also  in  a  whorl  of  three.  In  the  single  ovule  the  develop- 
ment of  the  megaspore  and  later  of  the  egg  is  similar 
to  that  in  the  Buttercup,  as  is  also  the  growth  of  the 
pollen  tube,  and  the  process  of  fertilization.  The 
endosperm  develops  as  a  belated  gameto- 

phyte,  and  the  zygote  divides  repeat- 
edly, eventually  becoming  a  small  stem 
with  a  root  at  one  end  and  a  single  ru- 
dimentary leaf  at  the  other.  Here  this  fig.  les.— Verti- 
embryo  sporophyte  continues  its  growth  flowl'r'^and^pi^tii)?* 
until  it  has  absorbed  all  of  the  endo- 
sperm: as  a  consequence  it  is  much  larger  than  in  the 
Buttercup,  and  the  seed  at  maturity  contains  no 
endosperm. 

526.  The  structure  and  behavior  of  the  fruits  (ripened 
carpels  with  their  contained  seeds)  are  in  no  wise  unlike 
those  in  the  Buttercup.  So  too  the  germination  of  the 
seed  inside  of  the  ripened  carpels  is  similar  to  what  has 
been  described  above.  However,  as  there  is  no  more 
endosperm  remaining  in  the  seed,  the  embryo  escapes 
from  it  shortly  after  the  root  has  appeared  and  pushes 
up  its  stem  and  leaves  to  the  light  above  ground,  as  an 
independent  plant  (sporophyte). 

527.  A  third  example  of  a  typical  flower  ma}^  be  seen 
in  the  Strawberry  (Fragaria)  in  which  the  flower  re- 
sembles that  of  the  Buttercup  and  the  Water  Plantain. 

19 


290  PHYLUAI  XIV.    AXTHOPHYTA 

Here  the  flower  axis  is  globularly  enlarged  somewhat  as 
in  the  Buttercup,  and  this  is  covered  likewise  with  many 
spirally  arranged  carpels  (megasporophylls).  At  the 
base  of  this  globular  body  of  carpels  the  axis  is  flattened 
out  into  a  rim  or  collar,  on  the  margin  of  which  the 
stamens  grow  in  several  whorls  of  5  or  10  each.  On 
this  margin  there  grow  also  the  five  rounded,  white  petals, 
and  the  five  pointed,  green  sepals,  both  series  in  whorls. 
The  development  of  the  single  ovules 
and   the  production    of  the   egg  are 


(S^ 


<^=^  essentially  the   same   as  in  the  two 

n^P£<^  preceding  examples.  After  fertiliza- 
tion the  zygote  develops  into  an  em- 
FiG  164— Vertical  plan  ^ryo  plant  cousistiug  of  a  small  stem 
pistu)!'^^"^  ^°"""  ^'""^  with  a  root  at  one  end  and  two  rudi- 
mentary leaves  at  the  other.  The 
endosperm  which  appeared  in  abundance  after  fertili- 
zation is  here  wholly  absorbed  by  the  growing  embryo, 
so  that  at  maturity  the  seed  contains  a  large  embryo, 
and  no  endosperm. 

528.  While  these  changes  are  taking  place  in  the  seed 
the  carpel  enlarges,  and  the  inner  layers  of  the  ovary 
cells  thicken  their  walls  into  sclerenchyma,  w^hile  the 
outer  layers  soften  into  a  juicy  flesh  (parenchyma).  The 
ripe  carpels  are  thus  very  small  fruits  consisting  of  a  thin 
flesh  surrounding  a  tiny  stone,  which  encloses  a  single 
seed.  The  proper  fruits  of  the  Strawberry  are  these 
small  ripened  carpels.  When  they  fall  to  the  ground  the 
contained  seed  germinates  by  pushing  out  the  root  of 
the  embryo,  and  since  there  is  no  remaining  endosperm 
this  is  quickly  followed  by  the  escape  of  the  remainder 
of  the  plant  from  seed  and  carpel,  when  it  pushes  its  stem 
and  leaves  into  the  light,  becoming  an  independent  plant 
(sporophyte). 


STRAWBiaiUY  291 

529.  Here  it  should  bo  said  that  in  the  Strawl)erry 
while  the  fruits  are  developing  the  gloi)ular  flower  axis 
enlarges  very  greatly,  and  its  tissues  become  soft  and 
juicy,  and  this  is  wdiat  we  eat  with  so  much  relish.  So 
the  ''strawberry"  as  we  eat  it  is  not  a 
fruit  properly  speaking.  It  is  a  thickened 
flower  axis  (stem),  covered  with  the  tiny 
proper   fruits,    popularly    supposed    to    ])e 

^^^^^'  Fig.  165.— Fm- 

garia    ("straw- 

Laboratory   Studies.     Xote:    In   connection  tnic^fVuit)^'^ 
with  the  anatomical  studies  of  special  plants 
suggested  below  the  student  is  referred  to  the  general  studies 
on  the  cell,   tissues,   and  tissue  systems,   already  taken  up  in 
Chapters  I,  II,  and  III  respectivel}'. 

In  working  out  the  following  studies  the  student  should  have 
before  him  specimens  of  the  three  plants  named  so  as  to  make 
comparative  studies  of  the  structures  represented  by  them. — 

(1)  Ranunculus,  (2)  Alisma,  and  (3)  Fragaria.  Where  these 
cannot  be  obtained,  acceptable  substitutions  may  be  made  as 
follows:  for  (1)  Myosurus,  Magnolia,  Caltha,  Hepatica, 
Anemone;  (2)  Sagittaria;  (3)  Potentilla,  Rubus,  Geuni, 
Duchesnea. 

(a)  Make  a  macroscopic  examination  of  the  stems  (of  the 
sporophytes)  noting  their  shape,  nodes,  branching,  bud  and 
leaf  arrangement,  and  follow  with  a  microscopic  examination  of 
(i)  a  cross-section  to  show  the  location  and  structure  of  the  vas- 
cular bundles,  and  the  distribution  of  green  and  colorless 
tissues;  and  (ii)  a  longisection  to  show  the  tissues,  epidermis, 
hairs  and  stomata. 

{}})  Examine  the  roots  (of  the  sporophytes)  and  note  whether 
there  is  one  main  root  (tap  root)  with  lateral  rootlets,  or  a 
cluster  of  roots  arising  from  about  the  same  point  on  the  stem. 
Note  the  shape,  size  and  character  of  the  roots  and  rootlets. 
Make  cross-  and  longisections  of  the  younger  and  older  parts 
and  a  longisection  of  the  tip  of  a  root,  to  study  the  location  and 
character  of  the  vascular  bundles,  the  kinds  and  distribution 
of  tissues,  the  origin  of  lateral  roots,  the  character  of  the  root 
cap,  etc. 


292  PHYLUM  XIV.     ANTHOPHYTA 

(c)  Make  a  similar  macroscopic  examination  of  the  leaves  (of 
the  sporophytes),  noting  whether  they  arise  singly  at  the  nodes 
("alternate"  leaves),  or  in  pairs  ("opposite"),  or  in  whorls  of 
three  or  more  ("whorled");  determine  the  shape  (sometimes 
variable),  margin,  surface,  size  and  variation  of  the  leaf  blades; 
the  length  and  shape  of  the  petioles;  and  the  shape  and  position 
of  the  stipules  (where  present).  For  the  microscopic  anatomy 
make  cross-sections  of  the  leaves  and  note  shape  and  size  of 
the  epidermal  cells,  thickness  of  cuticle,  character  of  hairs, 
type  and  location  of  vascular  bundles  (veins),  and  amount  and 
location  of  the  forms  of  parenchyma  tissue  (the  mesophyll) 
called  "pahsade"  and  "sponge"  parenchyma  respectively. 
In  cross-sections  of  the  petioles  note  size  of  intercellular  spaces. 
Make  sections  of  the  blade  parallel  to  the  surface,  and  note  the 
comparative  frequency  of  the  stomata  in  the  upper  and  lower 
epidermis,  shape  of  epidermal  cells  (and  correlation  with  type 
of  venation  if  any),  component  tissues  of  the  veins  and  the 
course  of  the  latter,  etc. 

(d)  Study  the  macroscopic  structure  of  the  flowers  observing 
them  from  above,  note  that  they  are  radially  symmetrical  (ac- 
tinomorphic).  Note  the  shape  of  the  axis  (torus)  and  how  the 
flower  parts  are  attached  to  it,  making  a  longitudinal  section  if 
necessarj^;  observe  that  it  does  not  surround  or  grow  fast  to 
any  floral  parts.  Note  the  number  and  arrangement  (in  spirals 
or  whorls)  of  the  megasporophylls  (carpels),  and  observe  that 
they  are  free  from  one  another  (apocarpous) ;  distinguish  the 
ovar}'  and  stigma  (and  style  if  present);  make  transverse  and 
longitudinal  sections  of  carpels  and  observe  number  and  loca- 
tion of  the  megasporangia  (ovules).  Count  and  note  arrange- 
ment (in  spirals  or  whorls)  of  the  microsporophylls  (stamens) ; 
examine  one  carefull}^  and  note  the  filament  (stalk)  and  anther 
(cluster  of  microsporangia);  section  transversely  an  unopened 
anther  and  note  the  four  microsporangia;  examine  the  mi- 
crospores (pollen)  from  a  mature  anther.  For  the  petals  note 
number,  shape,  color,  size,  and  particularly  their  arrangement 
(spirals  or  whorls).  Make  a  similar  study  of  the  sepals;  note 
whether  free  or  united;  observe  their  arrangement  with  refer- 
ence to  the  petals. 

(e)  The  study  of  the  female  gametophyte  will  require  the 
use  of  prepared  slides.  If  possible  they  should  show  the  devel- 
opment from  the  megaspore  mother-cell  (archespore)  to  four 


COMPARISON  OF  FLOWER  TYPES  203 

megasporcs,  thence  to  the  formation  of  the  immature  gameto- 
phyte  (embryo  sac)  with  its  egg,  arrangement  of  cells  and  nuclei 
being  noted.  A  slide  should  also  be  studied  in  which  a  young 
sporophyte  is  developing  amid  the  cells  representing  the 
further  growth  of  the  gametophyte  (i.e.  the  endosperm). 
The  male  gametophyte  may  also  be  studied  in  a  prepared  slide 
showing  microspores  (pollen  cells)  that  have  been  germinated 
so  as  to  show  the  tubular  antherids  (pollen  tubes)  and  which 
should  also  show  the  antheridial  nucleus,  and  the  generative 
nucleus  (or  possibly  the  two  non-ciliated  sperms  derived  from 

(/)  Strictly  considered  the  fruits  consist  of  the  modified 
carpels  containing  the  ripe  seeds,  but  any  accessory  modification 
of  adjacent  parts  should  also  be  noted.  Examine  the  flowers 
when  the  fruits  are  mature  and  note  the  structure  of  the  carpels, 
whether  dry  or  partly  fleshy,  and  dehiscent  (i.e.  opening  to  per- 
mit the  escape  of  the  seeds)  or  not  (indehiscent).  Note  (in 
Fragaria  or  Duchesnea)  the  considerable  enlargement  of  the 
torus,  and  consequent  separation  of  the  carpels.  Note  how  the 
calyx  is  modified,  and  whether  it  remains  or  falls.  Remove  a 
mature  seed  from  a  carpel  and  note  its  size  and  shape,  and  the 
external  characters  of  the  seed  coat  (consisting  of  the  integu- 
ments); section  it  transversely  and  longitudinally  and  deter- 
mine the  presence  or  absence  of  endosperm,  the  relative  size 
of  the  embryo,  and  the  number  of  cotyledons. 

530.  If  now  we  compare  the  three  flowers  described 
above  it  will  be  seen  that  they  are  very  similar.  Yet 
the  Buttercup  and  Strawberry  have  their  petals  and 
sepals  in  whorls  or  series  of  five  each,  while  they  are  in 
whorls  of  three  each  in  the  Water  Plantain.  Again  in 
the  former  there  are  tw^o  rudimentary  leaves  (''cotyle- 
dons") on  the  embryo  sporophyte,  wdiile  in  the  latter 
there  is  but  one.  Now  if  we  carry  our  comparison  to  the 
plants  bearing  the  flowers  we  find  other  differences.  The 
first  leaves  on  the  little  plant  in  the  Buttercup  and  the 
Strawberry  as  it  appears  above  ground  are  opposite  on  the 
stem,  while  in  tlie  Water  Plantain  thev  are  alternate, 


294  PHYLU.M  XIV.    ANTHOPHYTA 

and  continue  to  be  so  throughout  the  life  of  the  plant. 
In  the  first  two  the  vascular  bundles  of  the  leaves  are 
irregularly  netted  with  one  another,  while  in  the  Water 
Plantain  the  bundles  are  quite  as  markedly  parallel. 
Also  in  the  stems  of  the  first  two  there  is  a  more  or  less 
cylindrical  arrangement  of  the  vascular  bundles,  showing 
as  a  ring  in  a  cross-section,  while  in  the  Water  Plantain 
the  bundles  show  little  if  any  cylindrical  arrange- 
ment, the  bundles  being  more  or  less  scattered  through- 
out the  cross-section. 

531.  These  differences  are  pretty  constant  for  the 
plants  related  to  Buttercups,  Strawberries  and  Water 
Plantains  respectively,  so  that  botanists  have  been 
led  to  use  them  for  the  division  of  the  Flowering  Plants 
into  two  classes.  Thus  the  first  two  plants  and  their 
relatives  constitute  the  Class  Dicotyledoneae,  that  is  the 
plants  with  two  cotyledons,  while  the  Water  Plantains 
and  their  relatives  constitute  the  Class  Monocotyledoneae 
that  is  the  plants  with  one  cotyledon.  These  classes  are 
of  very  unequal  size,  the  Dicotyledons  containing  nearly 
109,000  species,  while  the  Monocot- 
yledons contain  somewhat  less  than 
24,000  species. 

632.  It  is  now  thought  that  the 
Dicotyledons  originated  earlier 
than  the  Monocotyledons,  and  that 
the  latter  must  be  considered  an 
^'''■Fiowe;[;.?p[an^s.*^'  early  offshoot  of  the  former.  Yet 
the  Monocotyledons  are  by  no 
means  higher  in  rank  than  the  Dicotyledons  as  a  whole; 
they  show  fewer  variations  from  a  common  type;  they 
are  more  nearly  uniform  in  structure  and  at  no  point  do 
they  rise  as  high  as  do  many  of  the  Dicotyledons.  For 
these  reasons  the  Monocotyledons  are  usually  discussed 


MONOCOTYLEDONS  295 

before  the  Dicotyledons,  as  a  lower  class,  in  sj)ite  of  the 
fact  that  they  appear  to  have  originated  from  the  latter. 
The  Dicotyledons  are  an  earlier  class,  but  they  have 
risen  higher  than  the  later  derived  Monocotyledons. 

CLASS  MONOCOTYLEDONEAE. 
The  Monocotyledons 

533.  Cotyledon  one;  leaves  on  the  stem  alternate; 
vascular  bundles  in  the  stem  scattered  (as  seen  in  cross- 
section),  in  the  leaf  blades  parallel  (''parallel-veined"); 
perianth  whorls  mostly  ternate  (in  3's). 

534.  There  are  seven  or  eight  types  (orders)  of  Mono- 
cotyledons. The  lowest  of  these  (Alifitnatales)  is  rep- 
resented by  the  Water  Plantain,  already  described. 
The  others  are  briefl}^  as  follows: 

535.  Lilies   (Liliales).     In  a  Lily  the  carpels   (mega- 
sporophylls)  have  been  reduced  to  three,  and  these  have 
grown  together  into  a  single  pistil  (''com- 
pound   pistil"),    in    which    each    carpel 
retains  its  ovule-bearing  cavity  (i.e.  the 
pistil  is  "3-celled").     The  stamens  (mi- 
crosporophylls)    are    in    two    whorls   of 
three  each:  the  petals  are  three;  and  the       p^^  ig7— Liiium 
sepals  three.     Commonly  the  perianth  is     ^vi'rse '^'Vansf  ^'^''"'*" 
relatively  large,   and  the  two  whorls  of 

similar  texture.  Throughout  the  flower  the  members  of 
successive  whorls  are  alternate. 

536.  The  flower  structure  here  reached  appears  to  be 
typical  of  the  great  body  of  the  Monocotyledons;  and  the 
structural  ]MH'uliarities  of  the  following  orders  are  only 
modifications  of  those  of  the  Lilies. 

537.  Calla  Lilies  (Aralcs).  In  the  Calla  Lilies  the 
individual    flowers    are  small,   and    massed    on  a    thick 


296  PHYLU^I  XIV.    AXTHOPHYTA 

stem,  commonly  diclinous  (i.e.  stamens  and  pistils  in 
separate  flowers,  monoecious  or  dioecious)  usually  sub- 
tended V)y  a  colored  leaf  (spathe).  Each  flower  is  like  a 
very  small  lily,  but  it  is  very  short  verti- 
cally, and  relatively  thick  ('"squatty")- 
The  short  stamens  are  usually  six,  and 
the  very  short-styled  pistil  is  3-celled  (or 
^i68"^aiia  l-ceflcd).  The  perianth  lobes  are  short, 
pSiKPoThTs).'"^  thick  and  fleshy  or  wanting.  Through- 
out the  order  (w^hich  is  largely  tropical) 
there  is  a  marked  tendency  toward  fleshiness  both  as  to 
the  plant  body  (always  herbaceous)  and  the  flowers. 

538.  Palms  {Palmales).  This  order  of  woody  trees 
and  coriaceous  leaves  has  small  flowers  resembling  those 
of  the  Lilies,  but  with  the  parts  usually  harder  and  more 
parchment-like  in  texture.  In  the  Coconut  the  flowers 
are  separated  (diclinous),  one  kind  having  functional 
stamens  (staminate),  and  the  other  a  functional  pistil 
(pistillate) .  The  staminate  flower  has  a  perianth  of  two 
ternate  whorls,  the  outer  (sepals)  shorter  than  the 
inner  (petals).  The  stamens  are  six  in  two  whorls,  and 
there  is  a  small,  tricarpellary  functionless  pistil.  The 
pistillate  flower  is  much  larger,  and 
has  a  perianth  of  two  ternate  whorls, 
the  sepals  and  petals  being  similar  to 
each  other.  There  are  no  stamens. 
The  large  pistil  is  tricarpellary  and 
should  contain  a  seed  in  each  of  the 

,         1       ,      ,  1  1  Fig.  169. — Palm  flowers 

carpels,    but    two    seeds   are    always  (Cocos). 

suppressed  and  their  carpellary  cavi- 
ties   are    crushed    by    the    growth    of  the    third    large 
seed.     The   fruit   has   much   the  structure  of  a  plum; 
in    which    the   inner   part   of  the   ovary   wall   becomes 
stony    (sclerenchyma),    while    the    outer    part   remains 


GRASSES 


2u: 


flesh}'  in  the  plum,  but  eventually  becomes  fibrous  in  the 
coconut.  The  coconut  of  the  northern  markets  is  the 
stone  of  the  ovary  wall,  containing  one  large  seed.  This 
stone  shows  its  tricarpellary  structure  by  the  ridges  on 
its  surface. 

539.  Grasses  {Graminales) .  In  these  plants  (includ- 
ing several  families)  the  stems  and  leaves  have  become 
elongated  and  markedly  fibrous  and  tough.  The  flowers 
are  of  the  Lily  type  but  much  reduced,  and  are  clustered 
uniformly  on  slender  axes  into  ''spikelets.'^  In  the 
Grasses  proper  (Family  Poaceae)  each  flower  is  in  the 
axil  of  an  outer  bract  (flowering  glume,  flowering  scale, 
lemma).  The  perianth  consists  of  a  scale-like,  2-keeled 
calyx  (palet,  palea)  representing  the  two  united  posterior 
sepals  (the  third  being  absent)  and  of  two  (anterior), 
rarely  three,  small,  flesh}^  petals  (lodicules).  Two  whorls 
of  three  stamens  each  are  present,  or  more  often  only 
the  outer  whorl.  The  pistil  is  tri- 
carpellary with  two  stigmas  (very 
rarely  three  stigmas)  and  there  is 
but  one  ovule  in  the  single  ovary 
cavit3\ 

540.  The  Bamboos  are  large, 
woody,  hollow-stemmed  tropical 
grasses,  in  which  the  corolla  is 
trimerous,  with  the  petals  (lodicules) 
relatively  large,  the  stamens  are  mostly  six,  and  the 
pistil  is  frequently  tristigmatic.  In  some  bamboos  the 
fruit  is  externally  flesh}',  while  in  others  it  is  like  that 
in  the  Brome  Grasses. 

541.  Brome  Grass  (Bromus)  has  a  hollow  herbaceous 
stem,  and  its  large  spikelets  are  several  flowered;  the 
corolla  is  reduced  to  two  small  petals  (lodicules) ;  the 
stamens    are    three,    and   the    pistil    has   two    feathery 


Fig.  170. — Grass  flowers 
and  spikelet. 


298  PHYLUM  XIV.    AXTHOPHYTA 

stigmas.     The  ripened  pistil  tightly  encloses  the  seed, 
forming  the  "grain"  or  ''caryopsis." 

542.  Maize  (Indian  Corn)  has  a  solid  (not  hollow) 
stem  and  its  spikelets  are  diclinous,  the  staminate  form- 
ing a  branching  inflorescence  at  the  top  of  the  stem,  the 
pistillate  being  crowded  upon  the  lateral  ''ears,"  which 
terminate  short  lateral  branches,  whose  numerous 
crowded  leaf  sheaths  form  the  ''husks."  The  staminate 
spikelets  are  in  pairs  (one  sessile,  the  other  stalked), 
and  each  is  two-flowered.  The  pistillate  spikelets  are 
also  in  pairs,  but  here  there  is  only  one  flower  in  each. 
The  styles  ("silks")  are  long,  and  bistigmatic.  The 
corn  "kernel"  is  the  ripened  ovary  with  its  tightly 
fitting  single  seed. 

543.  The  Sedges  (Family  Cyperaceae)  are  a  family 
of  widely  distributed,  somewhat  more  primitive,  grass- 
like plants  that  differ  in  vegetative  structure  from  the 
Grasses  in  that  the  leaves  are  three-ranked,  instead  of 
two  ranked,  and  the  stems  solid  instead  of  hollow.  The 
spikelets  more  often  have  the  bracts  spirally  arranged, 
only  a  few  genera  having  them  two-ranked  as  in  the 
grasses.  The  axillary  flower  consists  of  a  tri-  or  a  bicar- 
pellary  pistil,  six,  or  more  often  three,  stamens,  and  a 

perianth  of  two  ternate  whorls  of 
narrow  segments,  or  bristles  or  want- 
ing. The  ovary  wall  is  not  grown 
fast  to  the  single  seed. 

544.  Amaryllis    {Iridales).     In   the 

Amaryllis  the  flower  is  Lily-like  with 

Fig.  171.— Amaryllis      ^  ^^^^^  dcvclopcd  perianth  of  six  equal 

petaloid  segments  (sepals  three,  petals 

three),  six  stamens,  and  a  tricarpellary,  long-styled  pistil, 

whose  ovary  is  overgrown  by  the  receptacular  cup  which 

carries  up  the  perianth  and  stamens,  so  that  the  ovary 


ORCHIDS  299 

is  said  to  be  ''inferior.''  The  nearl}'  related  Iris  has  its 
sepals  reflexed  and  its  petals  erect:  its  stamens  are  three, 
and  the  three  style  branches  are  broad  and  spreading. 
The  ovary  is  inferior  as  in  Amaryllis. 

545.  Orchids  (Orchidales).  Here  the  ovary  is  in- 
ferior as  in  AmaryUis,  but  the 
perianth  is  made  up  of  unequal 
and  unlike  segments,  the  stamens 
are  reduced  to  two  or  one  (very 
rarely  three),  and  the  tricarpel- 
lary  pistil  has  but  two  functional 
stigmas  in  the  large  majority  of  ^'^-  ■^^fu^^nd  or  ^[pfP"^^ 
species. 

546.  In  all  the  foregoing  Monocotyledons  the  embryos 
have  one  cotyledon,  the  stems  have  scattered  vascular 
bundles,  the  leaves  are  alternate  on  the  stems,  and  paral- 
lel-veined, and  the  perianth  whorls  are  ternate. 

Laboratory  Studies.  Note:  In  these  studies,  and  those 
upon  Dicotyledons,  the  aim  should  be  to  bring  out  the  succes- 
sive advances  in  flower  structure  from  the  lower  to  the  higher 
forms.  With  this  object  in  view  many  other  details  may  well 
be  omitted,  but  some  attention  should  be  given  also  to  special 
modifications  of  the  general  plant  body. 

(a)  Make  cross-  and  longitudinal  sections  of  onion  seeds  and 
note  the  seed  coats  (integuments)  enclosing  the  rather  horny 
endosperm  witliin  which  lies  tlie  embrj'o  sporoi)hyte.  In 
similar  sections  of  grains  of  Indian  corn  the  external  coat  con- 
sists of  the  ovary  wall  grown  fast  to  the  integuments;  the 
remainder  of  the  grain  consists  of  endosperm  except  the  elon- 
gated or  shield-shaped  "germ,"  which  is  the  embryo  sporo- 
phyte. 

(6)  Sow  a  number  of  onion  seeds  and  grains  of  Indian  corn 
and  examine  one  of  each  every  day  after  germination  begins. 
In  the  onion  note  that  the  plantlet  "backs  out"  of  tlie  seed,  as 
it  were,  the  root  first  appearing,  followed  by  tlie  stem,  and  last 
of  all,  tlie  single  cotyledon.  In  the  corn  tlie  cotyledon  remains 
in  the  grain  as  a  si)ecial  absorbing  organ,  so  that  after  the  root 


300  PHYLUM  XIV.    ANTHOPHYTA 

emerges  the  leaves  appear,  the  short  stem  remaining  in  the  seed 
for  some  time  before  it  begins  to  elongate. 

(c)  For  the  lilies  use  any  true  lil}'  (Lilium)  or  one  of  the 
following:  Erythronium,  Yucca,  Allium,  or  TrilHum.  By 
longitudinal  and  transverse  sections  of  the  flowers  show  the 
single,  superior,  tricarpellary  pistil,  the  double,  trimerous 
whorl  of  stamens,  the  three  petals,  and  the  three  sepals. 

(d)  In  like  manner  examine  the  small  flowers  of  any  culti- 
vated ''Calla  Lily"  (or  Arisaema,  Pothos,  or  Acorus),  and  note 
also  the  thick  axis  (spadix)  on  which  the  flowers  are  collected, 
and  the  large,  subtending  bract  (spathe).  Look  for  more  or 
less  reduction  in  the  structure  of  the  flowers  in  some  of  these 
plants. 

(e)  The  lily-like  staminate  flowers  of  the  Coconut  (Cocos 
nucifcra)  should  be  studied  like  those  of  the  true  lilies  (c)  for 
general  plan,  and  the  pistillate  flowers  for  a  considerable  modi- 
fication of  that  plan.  Add  a  study  of  the  mature  nut.  The 
perfect  flowers  of  the  palmettos  (Sabal)  are  much  like  the 
staminate  flowers  of  the  coconut,  but  the  fruits  may  develop 
one,  two  or  three  of  their  carpels. 

(/)  Examine  segments  of  Bamboo  stems  for  woodiness.  Dis- 
sect Bamboo  spikelets,  noting  their  general  structure;  study  the 
flowers  with  their  nearly  complete  perianth  whorls,  three  or  six 
stamens,  and  two  or  three  stigmas. 

(g)  A  further  reduction  of  the  flower  structure  together  with 
a  typical,  not  much  reduced,  spikelet  structure,  may  be  found 
in  the  herbaceous  grasses  Bromus,  Poa,  Triticum,  or  Avena. 
Study  the  spikelet  structure,  and  then  the  flowers,  in  which 
both  perianth  whorls  are  incomplete,  one  whorl  of  stamens  is 
lacking,  and  the  pistil  has  but  two  stigmas.  Examine  also  the 
hollow  stem  (including  nodes  and  internodes)  and  leaves 
(including  sheaths  and  blades). 

(h)  Examine  the  solid  stem  (stalk)  of  Indian  Corn  (Zea) 
in  cross  and  longitudinal  sections,  and  also  the  leaves  and 
sheaths.  Dissect  a  staminate  spikelet  (from  the  ''tassel") 
with  its  two  tristaminate  flowers.  Dissect  out  from  a  young 
"ear"  a  pistil  with  its  long  stjde  ("silk"),  and  reduced  and 
distorted  scales  at  its  base. 

(i)  Examine  a  plant  of  Bulrush  (Scirpus)  and  note  arrange- 
ment of  leaves  on  the  solid  (parenchymatous)  stem,  and  the 
structure  of  blade  and  sheath.     Dissect  a  spikelet  (noting  its 


DICOTYLEDONS  301 

spiral  arrangement),  and  study  a  flower  with  its  tri-  or  bi- 
stigmatic  pistil,  three  stamens  and  (usually)  six  perianth  bris- 
tles. Cyperus  differs  mainl}-  in  its  two-ranked  spikelets,  and 
absence  of  perianth  bristles. 

(j)  Study  an  AmarylUs  flower  in  longitudinal  and  cross- 
sections  as  in  the  lily  (c).  The  small,  somewhat  zygomorphic 
flowers  of  the  banana  (Musa)  may  be  substituted  for  the  amar- 
yllis.  Note  the  absence  of  one  stamen.  Study  also  the  ma- 
ture fruit  (usually  seedless)  in  sections. 

(k)  Make  a  similar  study  of  the  Iris  flower. 

(l)  For  Orchids  the  Lady's  Slipper  (Cj^pripedium)  should  be 
studied,  and  its  two  stamens  grown  fast  to  the  tristigmatic 
style,  one  petal  slipper-shaped  (''lip"),  the  other  two  much 
like  the  pointed,  rather  elongated  sepals  (two  of  which  are  often 
united).  Note  the  sticky  pollen,  and  the  very  numerous,  mi- 
nute seeds.  For  this  may  be  substituted  the  native  Orchis,  or 
Ibidium,  or  various  greenhouse  orchids;  here  the  single  stamen 
is  attached  to  the  bistigmatic  style,  and  the  petals  and  sepals 
are  very  variable,  one  petal  ("lip")  being  always  much  longer 
and  more  showy. 

CLASS    DICOTYLEDONEAE. 

The   Dicotyledons 

547.  Cotyledons  two;  leaves  opposite  on  the  stem, 
later  ones  opposite  or  alternate;  vascular  bundles  in 
the  stem  arranged  cylindrically  (in  a  ring 
as  seen  in  cross-section) ;  vascular  bundles 
in  the  leaf-blades  irregularly  netted 
C'netted-veined");  perianth  whorls 
mostly  quinate  (in  5's). 

548.  There  are  two  greater  types  (sub-     grams   oV  '  flower 
classes)    of  Dicotyledons,  which  are  dis- 
tinguished by  the  structure  of  the  flower  axis,  as  follows: 

1.  Flower  axis  cyHndrical,  spherical,  hemispherical  or  flat- 
tened, bearing  on  its  surface  the  flower  parts  (perianth,  stamens 
and  carpels) "Axis  Flowers"  (Axiflorae). 

2.  Flower  axis  more  or  less  expanded  into  a  disk  or  cup, 


302  PHYLU.M  XIV.    AXTHOPHYTA 

bearing  on  its  margin  the  perianth  and  stamens,  subtending 
or  surrounding  the  carpels   .    . " Cup  Flowers"  (Calyciflorae) . 

.\xis  Flowers^ 


549.  The  Buttercup  (Ranunculus)  described  above  is 
one  of  tlie  simplest  of  the  Axis  Flowers,  in  which  the 
flower  axis  is  nearly  spherical. 

550.  The  Magnolia  flower  (Magnolia)  is  much  like  a 
gigantic  Buttercup,  the  axis  being  more  elongated,  but 
with  essentially  the  same  structural  plan.  This  flower 
also  has  many  separate  carpels. 

551.  The  common  Mallow  (Malva)  has  many  carpels 
in   a  single  whorl,  whose  adjacent  sides  feebly  cohere 

to  form  a  compound  pistil.  The  many 
stamens  also  cohere  below  into  a  tube,  but 
above  they  are  separate  and  spreading. 
The  perianth  whorls  are  dissimilar,  the 
outer  being  green  and  coarser,  and  the 
inner  white  or  bluish,  and  of  soft  texture. 
All  these  flower  parts  are  borne  on  the 
small,  conical  axis. 

552.  The  Wild  Geranium  (Geranium)  has  an  elongated 
axis  on  the  sides  of  which  is  borne  the  whorl  of  five 
feebly  adherent  carpels.  The  stamens  are  similarly 
reduced  in  number  (two  whorls  of  5  each)  and  the  per- 
ianth consists  of  dissimilar  whorls,  the  outer  of  green 
sepals,  and  the  inner  of  pink  or  purplish  petals. 

553.  In  the  Violet  (Viola)  the  axis  is  very  short  and 
bears  on  its  summit  the  tricarpellary  pistil.  The 
carpels  are  united  by  their  margins,  making  but  one 

^  For  the  more  systematic  arrangement  of  the  plants  in  this  and 
the  following  sub-class  the  reader  is  referred  to  the  outline  of  the 
Plant  Phyla  in  Chapter  XXII,  where  the  orders  and  families  are 
given  in  what  is  believed  to  be  their  proper  sequence. 


AXIS  FLOWERS  303 

pistil  cavity,  and  the  ovules  grow  upon  these  margins, 

i.e.  the  placentae  (the  areas  from  which  the  ovules  grow) 

are    '^parietal."      The   stamens  are 

five,  the  usually  blue  petals  five  and 

the  green  sepals  five.     In  all  violets 

the   front   lower   petal    is  large  and 

spurred  at  its  base,  the  side  petals 

are  smaller,  while  the  back  petals  are 

larger.     There  is  an  unUkeness  in  the 

petals,  and  the  flower  is 'irregular." 

554.  The  Mustard  flower  (Brassica)  has  reduced  the 
number  of  its  parts  still  further,  the  pistil  being  bicar- 
pellary.  Its  two  carpels  are  united  at  their  margins,  and 
the  ovules  grow  upon  these  margins  (parietal  placentae) , 
as  in  the  Violet.  Here,  however,  a  thin  membrane 
stretches  across  from  margin  to  margin  dividing  the  cavity 
into  two.  The  stamens  are  six  in  two  whorls  (4  and  2), 
the  yellow  petals  four,  and  the  green  sepals  four.  All 
of  these  parts  grow  upon  the  very  short  flower  axis. 

555.  In  some  Pinks  (Lychnis)  the  five-carpelled  pistil 
has  broken  away  the  partitions  between  the  carpels  so 

that  there  is  but  one  pistil  cavity, 
although  the  five  styles  indicate  its 
structure.  The  ovules  grow  upon  a 
central  column,  the  united  placentae. 
The  stamens  are  ten  (two  whorls),  the 

Fig.  i76.-Lychnis.  pctals  five,  and  the  united  green  sepals 
five    (gamosepalous).      In    some    other 

pinks  the  carpels  are  reduced  to  two,  but  the  flowers  are 

otherwise  like  those  of  Lychnis. 

556.  The  Primrose  flower  (Primula)  reminds  one  of  the 
pinks,  but  here  the  five  petals  have  grown  together  into  a 
tubular  corolla,  so  that  it  is  spoken  of  as  gamopetalous. 
The  pistil  is  composed  of  several  (probably  five)  carpels, 


304 


PH^XUIVI  XIV.     ANTHOPHYTA 


closely  fused  together,  and  their  partitions  have  broken 
away,  leaving  a  central  ovuliferous  column.  The 
stamens  are  five,  and  they  have  grown  fast  to  the  corolla 
tube.  The  sepals  are  five,  and  they  have  united  with  one 
another  for  some  distance  from  their  bases. 


Fig.   177. — Primula. 


Fig.   17S.— Phlox. 


557.  The  Phlox  (Phlox  )  again  reminds  one  of  the  pinks, 
and  primroses,  to  which  it  is  related.  The  corolla 
is  gamopetalous,  and  the  five  stamens  are  attached 
to  the  corolla  tube.  The  five  sepals  are  united  for  some 
distance  from  their  bases  (gamosepalous).  The  pistil 
is  reduced  to  three  carpels,  but  here  the  carpel  cavities 
persist,  and  in  each  there  are  from  one  to  four  ovules. 

558.  In  the  Petunia  (Petunia)  the  gamopetalous 
corolla  is  more  widely  open,  while  the  attachment  of  the 
five  stamens,  and  the  gamosepaly  of  the  calj^x  are 
like  those  of  phloxes  and  primroses.     The  reduction  in 

the  number  of  carpels  has  continued  so 
that  here  there  are  only  two,  each  with 
its  many-ovuled  cavity. 

559.  The  Snapdragon  (Antirrhinum)  has 
intensified  the   slight  irregularity  of  the 
corolla  of  the  Petunia  so  that  it  is  markedly 
2-lipped.     Its  stamens  which  are  attached 
to  the  corolla  are  reduced  to  four,  one  hav- 
ing disappeared.     The  pistil  is  bicarpellary,  and  the  seeds 
many  in  each  carpel  cavity.     The  calyx  is  gamosepalous. 
560.  The  Sage  (Salvia)  carries  the  preceding  modifi- 
cations a  step  further.     The    gamopetalous   corolla   is 


Fig.   170. 
Atitirrhinum. 


AXIS  FLOWERS  305 

strongly  2-  lipped,  and  its  attached  stamens  are  reduced 
to  two,    the    other     three     having     disappeared.     The 
bicarpellary  pistil  contains  two  ovules 
in   each   carpel   cavity.     The  calyx  is 
gamosepalous. 

In  the  Salvia  and  the  related  mints 
we  have  the  highest  development  of 
the  Axis  Flowers.  Compare  them  with 
the  Buttercups  and  Magnolias,  and  fig.^iso.— Sah 
note  what  changes  have  taken  place. 
The  axis  has  been  shortened  and  reduced;  the  carpels 
have  been  reduced  from  many  and  separate  to  two, 
united;  the  stamens,  from  very  many  to  two;  the  petals 
from  separate  (apopetalous)  to  united  (gamopetalous) ; 
as  well  as  from  regular  to  irregular;  the  sepals,  from 
separate  to  united. 

Laboratory  Studies,  (a)  Examine  externally  and  by  cross 
and  longitudinal  sections  the  seeds  of  Castor  Bean  (Ricinus), 
Pea  (Pisum),  and  Squash  (Cucurbita),  noting  the  character  of 
the  seed  coat;  the  presence  of  endosperm  in  Ricinus,  its  absence 
in  the  other  two;  and  the  two  cotj^ledons,  and  between  them  the 
rudiments  of  the  next  leaves  (the  plumule).  Where  the  endo- 
sperm is  lacking  note  that  the  cotyledons  are  thickened  into 
storage  organs. 

(b)  Germinate  some  of  the  foregoing  seeds,  examining  at 
frequent  intervals,  and  note  that  in  the  Castor  Bean  the  tliin 
cotyledons  remain  in  the  seeds  (in  contact  with  the  endosperm) 
for  a  longer  time  than  in  the  Squash,  but  eventually  in  both  they 
become  green,  and  function  as  leaves.  In  the  pea  the  hemi- 
spherical cotyledons  are  too  thick  to  function  as  leaves,  and 
remain  in  the  seed  coats. 

(c)  Examine,  in  sections  if  necessary,  a  flower  of  the  common 
Mallow  (Alalva),  or  of  Hollyhock  (Althaea),  or  Cotton  (Gossy- 
pium),  noting  number  and  arrangement  on  the  torus  of  the 
united  carpels,  united  stamens,  petals  and  sepals,  bearing  in 
mind  the  resemblance  toiind  dilTcrcnces  from  the  general  plan 
of  the  Buttercup  type  of  flower. 

20 


30G  PHYLUM  XIV.    ANTHOPHYTA 

(d)  In  a  similar  way  and  making  similar  comparisons  study 
the  flower  of  Wild  Geranium  (Geranium),  or  Cultivated 
Geranium  (Pelargonium). 

(e)  In  the  Violets  and  Pansy  (Viola)  make  out  especially 
the  structure  of  the  pistil  and  its  stigma,  the  fewer  stamens  (the 
two  lower  extended  backward),  and  the  zygomorphic  perianth. 

(/)  In  studying  the  flowers  of  Mustard  (Brassica)  or  of 
Radish  (Raphanus),  note  particularly  the  reduction  of  the 
general  flower-parts  to  fours,  with  the  carpels  and  outer  whorl 
of  stamens  further  reduced  to  two. 

(g)  In  the  Pinks  (using  Lychnis,  Silene  or  Dianthus)  observe 
the  disappearance  of  the  septa  in  the  ovary,  leaving  a  free 
central  placenta,  and  note  the  number  of  styles  and  number  and 
arrangement  of  the  stamens,  petals  and  (united)  sepals. 

(h)  For  the  Primrose  flower  (Primula)  make  out  the  pistil 
structure,  comparing  with  that  of  the  Pinks,  the  central  pla- 
cental column,  the  capitate  stigma,  the  five  stamens  attached 
to  the  tubular  spreading  corolla,  and  somewhat  united  sepals. 

(i)  Note  the  similarities  and  dissimilarities  in  the  structure 
of  the  flower  of  Phlox  as  compared  with  Primula. 

ij)  Study  the  funnel-shaped  Petunia  flower  noting  especially 
the  reduction  of  the  carpels  to  two  and  the  slight  zygomorphy 
of  some  of  the  corollas.  The  more  open  flower  of  Solanum,  or 
the  long-tubular  flower  of  Nicotiana  may  be  substituted  for 
Petunia, 

(k)  In  the  Snapdragon  (Antirrhinum)  in  addition  to  the 
marked  zygomorphy  of  the  corolla,  note  that  one  of  the  stamens 
(the  posterior)  has  disappeared.  Digitahs  with  similar  stamens, 
or  Pentstemon  with  four  fertile  and  one  sterile  stamen  may  be 
substituted  for  Antirrhinum. 

(/)  In  the  flowers  of  Sage  (Salvia)  or  Horsemint  (Monarda) 
note  the  strongly-marked  bilabiate  structure,  and  the  reduced 
number  of  stamens,  as  well  as  the  reduction  of  the  pistil  to  two 
bilobed,  biovulate  carpels.  In  Dead  Nettle  (Lamium)  the 
stamens  are  four  instead  of  two. 

Cup  Flowers 

561.  The  Strawberry  (Fragaria)  described  above  is 
one  of  the  simplest  of  the  Cup  Flowers;  in  fact  it  is  so 


CUP  FLOWERS 


307 


c^) 


Fig.  181. — Spiraea. 

On  the  margin 


simple  that  at  first  sight  we  scarcely  recognize  it  as  a  Cup 
Flower.  The  expanded  rim  below  the  globular  axis  is 
however  the  beginning  of  the  cup  form  of  the  flower  axis. 

562.  The  Spiraea  or  Bridal  Wreath  (Spiraea)  of  the 
gardens  shows  a  great  reduction  in  the  number  of  carpels, 
from  many  (in  the  Strawberry)  to  five 
each  with  several  ovules,  and  with  this 
we  have  the  disappearance  of  the  globular 
flower  axis,  while  the  fleshy  rim  or  disk 
has  now  become  somewhat  cup-shaped, 
of  the  cup  are  borne  the  many  stamens,  usually  20,  in 
whorls  of  5  or  10  each,  the  five  separate,  white,  rounded 
petals,  and  the  five  separate  pointed,  green  sepals. 

563.  The  Rose  flower  (Rosa)  show\s  a  considerable 
advance  over  that  of  the  Spiraea  in  its  general  structure 
although  more  primitive  as  to  its  carpels  and  stamens. 
The  cup  is  very  deep  and  completely  encloses  the  many 
free,  biovulate  (but  one-seeded)  carpels.  The  stamens 
are  very  many  (40-50,  or  more)  in  whorls  of  5  or  10, 
attached  to  the  cup  margin.  The  five  petals  are  large  and 
rounded,  and  with  the  pointed,  green  sepals  are  attached 
to  the  margin  of  the  cup.  After  flowering  the  cups  ri- 
pen into  edible,  fleshy  ''rose-apples." 


Fig.  182.— Rosa. 


Fig.  183.— Malus. 


564.  In  the  Apple  flower  (j\Ialus)  the  cup  is  still 
deeper,  narrower,  and  more  fleshy,  and  it  encloses  and  is 
grown  to  the  five,  slightly  united  biovulate  carpels. 
The  many  stamens,  20  or  more,  in  whorls  of  5  or  10  each, 


308  PHYLU:M  XIV.    ANTHOPHYTA 

are  borne  on  the  margin  of  the  cup,  and  liere  are  found  the 
five  round,  pinkish  petals,  and  the  five,  green-pointed 
sepals.  As  the  seeds  mature  the  tissue  of  the  cup  enlarges 
and  softens  into  the  flesh  of  the  ripe  apple,  while  the  five 
carpels  constitute  the  ''core.'^  Thus  in  the  apple  as  in 
the  strawberry  the  fleshy,  edible  tissue  belongs  to  the 
flower-axis,  and  not  to  the  proper  fruit  (the  core). 
In  fact  we  eat  the  cup  (flower  axis)  and  throw  the  fruit 
(core)  away! 

565.  In  the  Plum  (Prunus)  the  cup  has  become  deeper 
and  narrower  than  in  the  Spiraea,  while  the  carpels  are 

reduced  to  only  one  with  2  ovules. 
The  stamens  are  still  many,  20  or 
more  in  whorls  of  5  or  10  each,  on  the 
margin   of  the  cup,  while  the  petals 

Fig.   1S4. — Prunus.  ,  ,  .        ^     .  ,^. 

and  sepals  are  as  m  Spn-aea.  Ihe 
(free)  carpel  in  ripening  softens  and  thickens  its  outer 
tissues  into  an  edible  flesh,  while  the  inner  tissues  imme- 
diately surrounding  the  seed  are  hardened  into  a  stone 
(sclerenchyma). 

566.  The  Pea  flower  (Pisum)  has  a  shallow  cup,  and  in 
its  center  a  single  monocarpellary  pistil,  as  in  the  Plum 
flower.  Here,  however,  instead  of  two  ovules  there  are 
several,  so  that  the  pistil  becomes  elongated. 
The  stamens  on  the  margin  of  the  cup  have 
been  reduced  to  ten,  and  nine  of  these  have 
grown  together  by  their  filaments,  leaving 
one  free.  The  five  white  petals  are  unlike, 
so  that  the  flower  is  ''irregular."  The 
back  (upper)  petal  is  large  and  broad  (the 
''  banner"),  the  two  lateral  petals  (''wings")  are  narrower 
and  hooded,  while  the  two  lower  petals  are  still  narrower, 
united  along  their  lower  margins  and  much  curved 
upward    (forming    the    "keel").       The  green   calyx  is 


CUP  FLOWERS  309 

gamosepalous  and  nearl}^  regular.  The  carpel,  which  is 
somewhat  fleshy  when  young,  on  ripening  becomes  dry 
and  fibrous.     This  form  of  fruit  is  known  as  a  ''  legume." 

567.  It  should  be  noted  that  the  flowers  of  the  plum 
and  the  pea  are  very  much  aUke  in  plan,  the  greatest 
difference  being  the  irregularity  of  the  corolla,  and  the 
fewer,  united  stamens.  The  pea  represents  an  immense 
group  of  plants  (Bean  Family)  of  6,000  to  7,000  species, 
which  appear  to  have  been  developed  from  plum-like 
ancestors  by  their  corollas  becoming  irregular.  They 
constitute  an  evolutionary  side  line  in  which  irregularity 
of  the  corolla  C'zygomorphy")  has  been  especially 
developed  with  reference  to  insect  agency  in  pollination. 

568.  The  flower  of  the  Garden  Currant  (Ribes)   re- 
minds one  a  little  of  that  of  the  Apple.     Its  cup  is  deep 
enough  to  enclose  the  ovary  of  the  bicar- 
pellary  pistil.     The   carpels  are  united  at 
their   margins,   so   that   there    is    but   one 
cavity  with    two  parietal  placentae.     The         ^RibJg.^' 
margin  of  the  cup  bears  the  perianth  (five 

sepals,  five  petals)  and  the  five  stamens.  The  ovar}" 
in  ripening  thickens  and  softens  its  wall,  becoming  a 
many-seeded  berry,  a  portion  of  which  consists  of  the 
thickened  cup. 

569.  The  cup  of  the  Evening  Primrose 
(Oenothera)  is  ver}^  dee]),  not  only  en- 
closing the  quadricarpellary  ovary,  ])ut 
extending  as  a  tube  much  beyond  it.  The 
carpels  are  wholly  united  so  that  the 
ovary  has  four  many-seeded  cavities.  The 
eight  stamens  (in  two  whorls)  are  borne 
on  the  edge  of  the  tubular  cup,  as  are 
the  four  large  yellow  petals  antl  tlie  narrow,  greenish 
sepals.     The    ripening    ovary    becomes    hard    and    dry, 


310 


PHYLUM  XIV.     AXTHOPHYTA 


Fig.    ISS.— Opunti 


eventually  splitting  open  to  permit  the  escape  of  the 
seeds. 

570.  The  flower  of  the  Prickly  Pear  (Opuntia,  a  cactus) 
is  in  plan  much  like  the  preceding,  but  there  are  more 
carpels  (four  to  eight) :  these  are  united  at  their  margins, 

so  that  there  is-  but  one,  many-ovuled 
cavity,  with  four  to  eight  parietal 
l^lacentae.  The  cup  is  ver}-  fleshy,  and 
bears  on  its  margin  and  inner  face  the 
very  many  stamens,  many  petals  and 
many  sepals.  Cactuses  are  evidently 
related  to  the  Evening    Primroses,  but 

are  peculiar  in  being  very  fleshy,   and  mostly  leafless. 

The  stems  of  the  Prickly  Pear  when  young  bear  small 

leaves,  but  these  soon  dry  up  and  fall  off  after  which  the 

stems  are  leafless. 

571.  The  Walnut  flowers  (Juglans)  are  small  and 
diclinous,  those  with  stamens  being  in  drooping,  cylindri- 
cal,   crowded    clusters,    those    with 

pistils  soUtary  or  in  pairs.    Staminate 

flowers    with     a    reduced    perianth 

(calyx),   and   many    short    stamens; 

pistillate  flowers  with  a  bicarpellary       Fu-..  is9.— Jugians. 

pistil  which  is  wholly  covered  with 

the  thick  cup,  on  the  margin  of  which  are  four  reduced 

sepals,  and  as  many  very  small  petals.     The  fruit  is  fleshy 

externally  while  the  single  seed  is  surrounded  by  a  mass 

of  stone  tissue,  as  in  the  plum. 

572.  The  flowers  of  the  Oak  (Quercus)  are  much  like 
those  of  the  Walnut,  but  the  staminate  flower  clusters 
are  less  dense,  and  the  pistillate  flowers  are  solitary  in  scaly 
involucres  (i.e.  a  collection  of  several  to  many  crowded 
bracts).  The  staminate  flowers  have  a  reduced  perianth 
(calyx)  and  six  to  twelve  long  stamens,  while  the  single 


CUP  FLOWERS 


311 


pistillate  flower  in  each  scaly  cup-like  involucre  consists  of 
a  tricarpellary  pistil,  wholly  covered  by  a  thin  cup 
bearing  on  its  margin  the  very  minute  perianth  (calyx). 
The  fruit  is  a  thin,  tough-sholled  nut  C' acorn")  usually 
with  but  one  large  seed.  The  ripe  acorn  rests  in  the 
enlarged  scaly  involucre,  now  known  as  the  acorn  cup. 


Fig.   190.— Quercus. 


Fig.   101. — Pastinaca. 


573.  In  the  Parsnip  (Pastinaca)  the  small  flowers  are 
clustered  at  the  ends  of  slender  spreading  rays  (in  an 
umbel).  The  bicarpellary  pistil  is  covered  with  the  thin 
cup,  on  the  margin  of  which  are  the  five  very  minute 
sepals,  the  five  yellow  petals,  and  the  five  elongated 
stamens.  Each  carpel  cavity  contains  a  single  pendulous 
ovule.  In  ripening  the  bicarpellary  ovary  becomes  much 
flattened  (dorsally)  so  that  each  carpel  becomes  winged 
marginally,  and  later  the  two  carpels  split  apart. 

574.  The  flower  of  the  Honeysuckle  (Lonicera)  has  its 
bi-  or  tricarpellary  pistil  covered  with  the 

deep  cup,  as  in  the  preceding  plants.  The 
five  sepals  on  the  cup  margin  are  very  small, 
and  the  five  petals  are  united  into  a  tube 
which  widens  upward  to  its  irregular  mar- 
gin. The  five  stamens  are  attached  to  the 
inside  of  the  corolla  tube.  On  ripening, 
the  cup  and  enclosed  ovary  develop  into  a 
fleshy  few-seeded  ])erry. 

575.  In  the  Sunflower  (Helianthu.s)   which   is  one 
the  lowest  members  of  the  highest  order  {Adeniles) 


312  PH^XUM  XIV.    ANTHOPHYTA 

Flowering  Plants  the  small  flowers  are  clustered  into 
many-flowered  heads,  from  which  fact  these  plants  and 
their  relatives  are  known  as  'X'omposites."  The  face 
or  top  of  the  head  is  flat,  and  its  back  is  covered  with 
many  spreading,  green  bracts,  constituting  the  '^invo- 
lucre." The  face  of  the  head  bears  the  many  small 
crowded  flowers  each  in  the  axil  of  a  stiff  bract.  Those 
on  the  margin  (''ray  flowers")  are 
quite  sterile,  and  have  large  flat 
corollas  (of  five  petals  united  below 
into  a  tube,  but  "ligulate"  above), 
while  the  remainder,  ("disk  flowers") 
produce  seeds  and  have  tubular 
Fig.  i93.-Heiianthus.  corolks.  Examining  one  of  the 
latter  we  find  that  the  bicarpellary  pistil  is  wholly 
covered  by  the  thin  cup:  the  calj^x  ("pappus")  is  re- 
duced to  two  or  a  few  scales :  the  corolla  consists  of  five 
petals  united  into  a  tube  which  is  five-pointed  at  its 
summit:  the  five  stamens  are  borne  on  the  inside  of  the 
corolla  tube,  and  the  anthers  are  united  by  their  mar- 
gins into  a  tube  which  surrounds  the  style.  The  pistil 
has  a  long  style  which  divides  above  into  two  recurved 
style  branches,  each  stigmatic  on  its  upper  surface. 
There  is  but  one  erect  ovule  at  the  base  of  the  single 
cavity  of  the  ovary.  On  ripening  the  cup  and  ovary  wall 
become  tough  and  leathery,  and  closely  surround  the 
relatively  large  seed,  and  this  structure  is  known  as  an 
"achene." 

576.  The  Dandelion  flower  head  (Taraxacum,  or  Leon- 
todon)  is  in  plan  much  like  that  of  the  Sunflower,  but  here 
the  flowers  all  have  flat  (ligulate)  corollas,  and  all  produce 
seeds.  Each  flower  consists  of  a  bicarpellary  ovary  which 
is  wholly  covered  by  the  thin  cup,  on  whose  upper  margin 
is  the  whorl  of  many  fine  bristles  (the  calyx,  or  pappus), 


CUP  FLOWERS  313 

and  the  five-petaled  corolla,   tubular  below,   but  open 

and  flat  above.     The  five  stamens  are  borne  on  the  inside 

of  the  tubular  part  of  the  corolla,  and  their  anthers  are 

united  around  the  style,  as  in  the 

Sunflower.      The  ovule   also   is 

quite  like  that  in  the  Sunflower. 

On  ripening  the  upper   part  of 

the  cup  becomes  prolonged  into 

a   slender   beak  far  beyond  the 

ovary    carrying    the    spreading         ^^^  ^^^ 

calyx   whorl    upon    its    summit, 

and  forming  a  veritable  parachute  which  readily  carries 

away  the  achene  and  its  seed  in  even  the  lightest  of 

breezes. 

577.  Here  it  may  be  remarked  that  the  Dandelion 
shows  the  highest  development  of  flower  structure  found 
in  the  Anthophyta,  and  so  it  may  be  considered  as  the 
highest  plant  in  the  Vegetable  Kingdom. 

Laboratory  Studies,  (a)  With  longitudinal  sections  of  the 
flowers  of  Spiraea  make  out  especially  the  thickened  cup  (torus), 
the  smaller  number  of  several-seeded  carpels  (five),  and  the 
man}'  stamens. 

(6)  Examine  externally  and  in  longitudinal  section  flowers 
and  "apples"  of  any  rose  (Rosa).  Note  the  great  number  of 
one-seeded  carpels  (resembling  those  of  Strawberry),  and  sta- 
mens, and  the  deeply  hoUowed  out,  fleshy,  receptacular  cup, 
comparing  with  S])iraea. 

(c)  Making  comparisons  with  the  Rose  examine  in  a  similar 
way  tlic  flowers  and  fruit  of  the  Apple  (Mains),  or  Pear  (Pirus), 
Quince  (Cydonia)  or  Hawthorn  (Crataegus),  noting  especially 
the  great  thickening  of  the  torus  and  its  adherence  to  the  five 
united  carpels. 

(d)  Make  vertical  sections  of  Plum  flowers  (Prunus)  so  as 
to  show  the  single  free  pistil  (of  one  carpel)  at  the  bottom  of  the 
cup,  and  the  many  stamens  on  its  margin.  Make  cross-sections 
of  growing  ])lums  (fruits)  showing  stony  cndocarp,  and  fleshy 


314  PHYLUM  XIV.    AXTHOPHYTA 

exocarp.  Cherry,  Peach  or  Almond  flowers  and  fruits  may  be 
Bubstitiited  for  the  Plum. 

(e)  Dissect  a  flower  of  the  Garden  Pea  (Pisum)  so  as  to  show 
the  zygomorphy  of  the  corolla,  the  ten  curved  stamens,  the 
single,  elongated  and  several-ovuled  pistil.  Study  developed 
pods  (legumes)  and  young  seeds.  Comi)are  the  zygomorphic, 
shallow-cupped  Pea  flower  with  the  related  actinomorphic 
Plum  flower.  The  Sweet  Pea  (Lathyrus),  Bean  (Phaseolus), 
and  Locust  (Robinia)  flowers  are  similar  to  those  of  the  Pea. 

(/)  Study  the  flowers  and  fruits  of  the  Currant  or  Gooseberry 
(Ribes),  observing  their  general  resemblance  to  the  Apple,  but 
noting  the  bicarpellary  pistil  with  parietal  placentae  and  the 
reduced  number  of  stamens. 

ig)  Compare  the  flower  of  Oenothera  with  that  of  Spiraea 
noting  the  extreme  elongation  of  the  receptacular  cup,  which 
adheres  to  the  united,  many-seeded  carpels;  and  the  reduction 
of  the  stamens  to  two  whorls. 

(h)  Study  macroscopically  the  mature  sporophyte  of  a 
Prickly  Pear  (Opuntia),  noting  the  small,  narrow,  fleshy,  short- 
lived leaves  on  the  young  shoots.  In  longitudinal  and  cross- 
sections  of  the  flowers  make  out  the  fleshy  cup  surrounding  the 
compound  ovary,  and  the  many  spirally  arranged  stamens, 
petals  and  sepals.  Other  genera  of  cactuses  show  a  similar 
flower  structure,  and  may  be  substituted  for  Opuntia,  but  the 
plants  are  mostly  wholly  leafless. 

(i)  Examine  macroscopically  a  staminate  flower  cluster  (cat- 
kin) of  the  Walnut  (Juglans)  or  Hickory  (Hicoria)  noting  the 
crowded,  small,  many-stamened,  apetalous  flowers.  IMake 
cross  and  longitudinal  sections  of  the  pistillate  flower  showing 
the  inferior  ovary,  surmounted  by  two  large  stigmas.  Make 
comparative  studies  of  the  fruits  and  nuts. 

if)  Examine  the  staminate  flower  clusters  of  the  Oak 
(Quercus)  or  Chestnut  (Castanea),  comparing  the  several 
staminate  flowers  with  those  of  the  preceding  (i).  As  the 
leaves  are  unfolding,  or  soon  after,  find  near  the  tips  of  the 
twigs  the  clusters  of  two  or  three  pistillate  flowers.  Dissect 
these  out  from  their  involucres,  and  note  the  calyx  borne  on 
the  edge  of  the  thin  receptacular  cup  which  adheres  to  the  tri- 
carpellary  ovary.  Examine  ripe  acorns  which  are  found 
single  seated  in  the  cup-like  involucre,  or  chestnuts  which  occur 
several  together  entirely  enclosed  in  the  prickly  involucre. 


SUMMARY  OF  ANTHOPHYTA  315 

(k)  In  examining  the  flowers  of  the  Parsnip  (Pastinaca), 
note  first  the  umbellate  inflorescence,  and  then  dissect  out  a 
little  flower,  noting  especially  the  very  small  vestiges  of  sepals. 
8tudy  the  matured  fruit  noting  that  it  splits  vertically  into 
two  halves.  The  Carrot  (Daucus)  or  Cow  Parsnip  (Heracleum) 
may  be  substituted  for  the  Parsnip. 

(l)  Make  dissections  of  the  flowers  of  the  Honeysuckle 
(Lonicera),  Snowberry  (Symphoricarpos)  or  Elder  (Sambucus) 
and  note  the  few-celled,  few-seeded,  inferior  ovary,  very  small 
sepals,  and  the  somewhat  zygomorphic  (regular  in  Sambucus) 
corolla  of  united  petals,  upon  which  are  borne  the  few  stamens. 

(m)  Make  a  macrosco])ic  examination  of  a  Sunflower  head 
(Helianthus),  noting  the  involucre  of  green  bracts  on  the  back, 
the  marginal  row  of  ligulate  flowers  (''rays"),  and  the  central 
mass  ("disk")  of  tubular  flowers.  Dissect  out  and  examine 
carefully  an  individual  flower  of  each  kind,  noting  particularly 
the  calyx  (''pappus"),  and  inferior,  bicarpellary,  one-seeded 
pistil.  Dissect  a  mature  achene  ("seed").  Rudbeckia  or 
Coreopsis  maj^  be  substituted  for  Helianthus. 

(n)  Study  the  flower-head  of  the  Dandelion  (Taraxacum 
or  Leontodon),  comparing  it  with  that  of  the  Sunflower.  Note 
the  following  points  of  difference:  the  development  of  the  cor- 
ollas of  all  flowers  into  ligules,  fertility  of  all  flowers,  develop- 
ment of  calyx  (pappus)  as  a  whorl  of  numerous  fine  bristles, 
and  absence  of  bracts  subtending  each  flower.  Examine  a 
fruiting  head.  Note  the  presence  of  latex  in  the  plant.  Wild 
or  cultivated  Lettuce  (Lactuca)  may  be  substituted  for  the 
Dandelion. 

Summary  of  Anthophyta 

578.  Looking  ])ack  over  the  Flowering  Plants  it  is 
seen  that  their  simpler  forms  are  like  those  of  Buttercups 
and  their  near  relatives,  and  that  from  this  primitive 
type  there  have  arisen  three  diverging  phyletic  groups. 
One  of  these  (the  Monocotyledons)  begins  with  the 
Water  Plantains,  and  culminates  in  the  Orchids:  another 
(the  Axis  Flowers)  begins  with  the  Buttercups  and 
passing  through  various  intermediate^  forms  culminates  in 


316  PHYLUIvI  XIV.    AXTHOPHYTA 

the  flints:  while  still  another  (the  Cup  Flowers)  begins 
with  the  Strawberries  and  culminates  in  the  Sunflowers 
and  Dandelions.  It  will  be  noted  furthermore  that  the 
Axis  Flowers  and  Cup  Flowers  agree  in  regard  to  their 
cotyledons,  arrangement  of  leaves,  vascular  bundles  of 
stems  and  leaves,  and  perianth  whorls,  causing  us  to 
consider  them  as  two  subdivisions  of  a  common  class, — 
Dicotyledons, —  coordinate  with  the  Monocotyledons. 

579.  Taking  a  longer  look  backward  it  may  be  seen 
that  in  the  Anthophyta  we  have  the  culmination  of  the 
evolutionary  tendencies  manifested  in  the  main  line  of 
plant  progress  over  which  we  have  travelled: — from 
Myxophyceae  to  Chlorophyceae,  thence  to  the  lower 
Bryophyta,  and  from  these  to  the  Old-fashioned  Ferns 
(Pteridophyta)  and  from  these  again  to  the  Seed  Ferns 
and  Flowering  Plant  Ancestors  (in  Cycadophyta),  from 
which  the  step  is  relatively  short  to  the  simpler  Flowering 
Plants.  It  follows  that  but  five  of  the  preceding  phyla 
have  contributed  to  the  development  of  the  Flowering 
Plants,  and  that  the  eight  remaining  phyla  are  side 
branches  whose  developmental  accretions  added  nothing 
that  continued  to  the  Flowering  Plants.  These  five 
contributing  phyla  contain  somewhat  less  than  one-fourth 
of  the  non-flowering  plants,  and  yet  it  may  be  doubted 
whether  even  more  than  one-fifth  of  these  again  con- 
tributed in  any  way  to  the  structure  of  the  Flowering 
Plants.  So  we  may  say  that  of  the  approximately 
100,000  plants  in  the  thirteen  phyla  preceding  Antho- 
phyta, probably  no  more  than  5,000  represent  structures 
in  any  sense  ancestral. 

580.  It  will  be  instructive  to  enumerate  the  greater 
steps  in  this  progressive  development  from  the  Myxo- 
phyceae to  Anthophyta,  as  follows: 


STEPS  IN  DEVELOPMENT  317 

Myxophyceae,  contributed  first  of  all  the  cell  unit,  to  which 

they  added  a  definite  nucleus,  and  definite  plastids. 
Chlorophyceae,  carried    the   plant  body  from  the  single  cell 

to  the  rooted,  branched  fdament, 
— added  ciliated  gametes, 

— carried  generation  homisogamy  to  heterogamy, 
— carried    the    result    of    fertihzation    from    the    simple 

zygote  to  the  simple  fruit. 
Bryophyta,  developed  the  plant  body  as  a  cell  77iass, 
— developed  the  sporophyte  from  the  simple  fruit, 
and  so  brought  in  an  obvious  alternation  of  generations, 
and  with  it  terrestrial  life, 
with   which    came    the   beginning    of   supporting   tissues 

(woody  strands), 
and   simultaneously   the  beginning   of  conducting  tissues 

{vascular  strands). 
Pteridophyta,   reduced  the  gametophyte  to  a  smaller  and 

short-lived  structure, 
— developed  an  independent  sporophyte  by  the  production 

of  roots  and  leaves; 
— differentiated  isospores  into  heterospores;  (microspores 

and  megaspores); 
— perfected  the  supporting  tissues  (woody  stratids); 
— perfected  the  conducting  tissues  (vascular  bundles). 
Cycadophyta,  developed  special  sporophylls  for  megaspores 

( megasporophylU) , 
— retained  the  megaspore  in  the  megasporangium, 
— which  became  covered  ])y  an  indusium  (integument), 
— reduced  the  archegonial  gametophyte  to  a  dependent 

structure  retained  by  the  megasporangium, 
— which  led  to  the  development  of  the  seed, 
— developed  special  sporophylls  for  microspores  (micro- 

sporophylls), 
— developed  tubular  antherids, 
— reduced  the  sperms  to  two, 

— aggregated  the  sporophylls  into  a  cone  (strobilus); 
— developed  the  beginnings  of  the  perianth, 
— produced  an  erect,  long-lived  stem, 
— developed  fihro-vascular  bundles, 

and  modes  of  thickening  the  stem. 


318  PHYLUM  XIV.    ANTHOPHYTA 

Anthophyta,  developed  inicrosporophylls  into  stamens, 
— reduced  the  sperms  to  non-ciliated  cells, 
— developed  megasporophylls  into  jnstils, 
— developed  a  proper  perianth, 
— perfected  fihrovascular  bundles, 

arranging  them  in  a  cylinder, 
— perfected  the  thickening  of  the  stem, 

by  fihrovascular  and  interfascicular  cambium,. 


LITERATURE  OF  ANTHOPHYTA 

J.   M.   Coulter  and   C.   J.    Chamberlain,    Morphology    of 

Angiosperms,  New  York,  1903. 
N.  L.  Britton  and  Addison  Brown,  Illustrated  Flora  of  the 

Northern  States  and  Canada,  Second  Edition,  New  York, 

1913. 
N.  L.  Britton,  Manual  of  the  Flora  of  the  Northern  States 

and  Canada,  Second  Edition,  New  York,  1905. 
B.  L.  Robinson  and  M.  L.  Fernald,  Gray's  New  Manual  of 

Botany,  New  York,  1908. 
J.  K.  Small,  Flora  of  the  Southeastern  United  States,  Second 

Edition,  New  York,  1913. 
J.  M.  Coulter  and  Aven  Nelson,  New  Manual  of  Botany 

of  the  Central  Rocky  Mountains,  New  York,  1909. 
F.  E.  and  E.  S.  Clements,  Rocky  Mountain  Flowers,  New 

York,  1914. 
T.  C.  Frye  and  G.  B.  Rigg,  Northwest  Flora,  Seattle,  1912. 
L.  R.  Abrams,  Flora  of  Los  Angeles  and  Vicinity,  Stanford 

University,  1911. 


CHAPTER  XXI 
SO:\IE  SPECIAL  ADAPTATIONS 

681.  The  plant  body  (sporophyte)  of  the  Anthophyta, 
while  standardized  as  to  general  plan,  is  very  plastic  as 
to  the  details  of  its  structure.  This  plasticity  has  enabled 
it  to  respond  so  fully  to  various  needs  as  to  bring  about 
marked  changes  in  its  size,  form,  proportions  of  parts, 
surface  characters,  etc.  Only  the  more  important  of 
these  need  be  noticed  here. 

582.  For  particular  purposes  some  parts  of  the  plant 
body  may  have  a  special  development,  as  the  thorny  (not 


Fig.  195. — Standard     Fig.   190. — Runners,  above 
plant  (Anthophyta).  and  under  ground. 


Fig.  197  — Corm,  bulb, 
and  root. 


parenchymatous)  leaves  of  the  Barberry,  the  thorny 
leafless  branches  of  the  Honey  Locust  (both  protective), 
the  runners  of  the  Strawberry  above  ground,  and  the 
under-ground  rootstocks  of  the  Canada  Thistle  (both  for 
vegetative  reproduction) . 

583.  Many  plants  store  up  food  substances  in  some 
part  of  the  i)lant  body,  resulting  in  considerable  changes 
in  form.  Thus  the  lower  part  of  the  stem  may  be 
spherically  enlarged,  as  in  the  so-called  corms  of  Arisaema 
and   Gladiolus.     In  the  bulbs  of  iiuiiiy   plants,   as  the 

319 


320  SOME  SPECIAL  ADAPTATIONS 

Onion,  and  Hyacinth,  the  food  substances  are  stored  in 
the  thickened  leaf  bases.  Turnips,  radishes,  dahUas, 
etc.,  store  their  food  substances  in  tlieir  roots  which  are 
accordingly  much  thickened.  Other  plants  develop 
the  ends  of  their  rootstocks  into  storage  structures,  as 
the  tubers  of  the  potato  and  Jerusalem  Artichoke;  while 
again  some  thick  leaves,  as  those  of  the  Century  Plant 
(Agave),  and  many  other  Monocotyledons,  are  storage 
organs. 

584.  Habitat.  Most  flowering  plants  grow  with  their 
roots  in  moist  (not  wet)  soil,  with  their  leaves  in  air  of 
moderate  humidity.  Stated  otherwise  we  may  say  that 
under  these  conditions  the  great  majority  of  flowering 
plants  developed  the  forms  which  they  have.  So  when 
we  say  that  such  plants  are  '^mesophytes"  we  are  merely 
stating  the  fact  that  the  majority  of  plants  live  under 
these  quite  similar  conditions.  And  these  have  the  usual 
leaves  and  stems.  A  much  smaller  number  have  been 
able  to  live  in  drier  soil  and  drier  air,  their  leaf  surfaces 
being  smaller  or  wanting,  their  epidermis  thicker,  their 
tissues  harder,  and  these  we  have  denominated  ''xero- 
phytes,"  literally,  dry  plants.  On  the  other  hand  some 
plants  have  been  able  to  live  partly  or  wholly  in  the 
water.  Their  stems  and  leaves  are  weak  and  soft  and 
their  submerged  leaves  reduced  (dissected).  Such  plants 
we  have  called  '^ hydrophytes"  (i.e.  water  plants). 
Other  adaptations  still  less  marked  have  been  noticed,  as 
the  ^'halophytes"  of  salt  waters  or  soils,  the  ''ruderal 
plants"  of  waste  places,  ''shade  plants,"  ''sun  plants," 
etc. 

585.  Here  may  be  noted  the  mocUfications  of  the 
plant  body  following  the  acquisition  of  a  parasitic  habit. 
These  are  well  illustrated  in  the  common  Dodder  (Cus~ 
cuta,  a  climbing  vine  related  to  the  Morning  Glories) 


AXKMOPIIILY 


321 


Fig.   198. 

Morning    glory 

and  dodder. 


which  has  lost  its  leaves,  its  ^reen  color,  and  its  firm  stem 
structure.  The  Broom-rapes  {Orohanchaceae)  likewise 
have  bract-like,  chlorophyll-less  leaves. 
And  so  the  saprophytic  Indian  Pipes  {Mon- 
otropaccae)  show  a  similar  reduction. 
Somewhat  allied  to  these  modifications 
are  those  in  the  case  of  the  so-called  In- 
sectivorous plants  where  the  leaves  are  modi- 
fied into  pitchers,  or  other  structures  for  the 
capture  or  digestion  of  insects. 

586.  In  their  evolution  from  the  primitive  type  of 
flower  to  the  more  derived  structures  the  Flowering 
Plants  have  produced  a  multitude  of  forms  of  flowers 
many  of  which  show  themselves  extremely  well-fitted  for 
certain  very  definite  conditions.  It  is  in  connection 
with  the  methods  of  pollination  that  the  greatest  varia- 
tion is  shown.  It  seems  certain  that  the  primitive  flowers 
were  dependent,  as  are  the  vast  majority  of  flower  types 
now,  upon  the  aid  of  insects  in  pollination.  However, 
very  numerous  groups  of  Flowering  Plants  have  given 
up  this  so-caUed  ''entomophilous"  habit,  and  are  polli- 
nated by  the  wind  (''anemophilous").  Such 
flowers  are  usually  marked  by  certain  charac- 
ters in  common,  viz.  the  abundance  and 
lightness  of  the  pollen,  the  occurrence  of  the 
staminate  flowers  in  hanging  clusters,  "cat- 
kins" (easily  swung  by  the  wind,  as  in  the 
Walnut,  Oak,  etc.) ;  or  with  the  branches  or 
inflorescence  slender  and  swinging  easily  in 
the  wind  (as  in  various  grasses);  the  styles 
and  stigmas  are  usually  very  large,  thus  exposing  more 
surface  on  which  the  chance  pollen  grains  may  be  caught; 
usually  too  the  pistils  have  but  one,  or  very  few  ovules, 
for  each  ovule  requires  a  pollen  grain  for  its  fertilization 

21 


322  SOME  SPECIAL  ADAPTATIONS 

and  the  chances  are  fewer  for  a  multiple  pollination  by 
wind-blown  pollen.  Wind-pollinated  flowers  are  usually 
small  and  dull  in  color. 

587.  On  the  contrary  the  insect  (and  bird)  pollinated 
flowers  are  usually  bright  colored  (and  it  has  been  found 

that  many  insects  are  attracted  long  dis- 
tances by  bright  colors).  They  are  usually 
large  enough  to  be  easily  visible,  or  if 
small  are  bunched  in  large,  conspicuous 
masses  (as  in  Elder).  If  not  showy  them- 
FiG.  200.— Dog-  selves  they  are  often  bordered  by  showy 
leaves  (as  in  Snow-on-the-Mountain  Eu- 
phorbia margi7iata),  or  some  of  the  flowers  are  con- 
verted into  showy  structures  at  the  sacrifice  of  their 
sexual  function  (e.g.  marginal  flowers  of  some  Dog- 
woods). In  addition  to  these  it  is  usual  for  entomophi- 
lous  flowers  to  emit  perfumes  of  various  kinds,  some 
of  which  are  perceived  by  insects  at  great  distances. 
Some  of  these  are  very  unpleasant  to  man,  but  are 
attractive  to  certain  insects,  e.g.  StapeUa,  whose  car- 
rion-like odor  is  attractive  to  carrion  insects. 

588.  Within  the  flowers  are  developed  the  secretory 
glands  which  secrete  a  sugary  liquid.  Attracted  by 
color  and  odor  the  insects  fly  ito  the  flowers  and  seek  out 
this  nectar  which  they  imbibe.  In 
so  doing  they  come  in  contact  wdth 
the  stamens,  and  become  powdered 
with    pollen,    and   later  touch   the       t.     „^,     ^     ,     . 

.      .,  1  •    1        1  ^'°-   201.— Regular    (ac- 

piStll  to  which  the  pollen  is  trans-  tinomorphic)  and  irregular 
^  ^  (zygomorphic)  flowers. 

f  erred.       In    flowers    with    many 
stamens   and   pistils   the   nectaries  are  usually   several 
in  all  the  radii  of  the  flower,  and  the  insect  in  visiting 
will  manage  to  become  thoroughly  covered  with  pollen 
and  to  put  it  on  the  summit  of  the  stigma.     In  many 


ZYGOMORPHY  AND  DIIVIORPHISAI  323 

flowers,  however,  the  stamens  are  few,  and  the  pistils 
few  or  only  one.  Here  often  the  flowers  become  one- 
sided (zygomorphic),  of  such  a  structure  that  access  to 
the  nectary  can  be  obtained  only  at  such  a  point  that 
polhnation  is  rendered  all  the  more  certain.  In  this 
connection  adaptation  of  flowers  to  certain  insects  is 
very  apparent.  Thus  certain 
orchids  are  of  such  a  structure 
that  only  certain  butterflies  or  bees 
can  reach  the  nectary,  and  in  so 
doing  pollinate  the  flowers.  Other  W  _^_  ^ 
insects  either  cannot  reach  it  at  I'  \^  ''^^^^^:^^=' 
all,  or  in  so  doing  fail  to  remove     ,,      ono    t>  * 

'  ^  Fig.    202. — Proterogvnoua 

the     pollen     or     transfer     it     to     the     (Plantago)      and      proteran- 
'^  drous  (Llaytonia)  flowers. 

stigma. 

589.  In  connection  with  entomophily  it  was  early  ob- 
served that  many  flowers  were  of  such  structure  that  self- 
fertilization  (i.e.  polhnation  with  pollen  of  the  same 
flower)  is  impossible.  Thus  in  the  majority  of  such 
flowers  the  pollen  is  all  shed  before  the  stigma  is  recep- 
tive (proterandrous),  or  much  less  frequently  the  stigma 
passes  the  receptive  stage  before  the  pollen  is  set  free 
(proterogynous).  In  some  plants  the 
flowers  are  ''dimorphic,"  i.e.  on  certain 
individuals  the  stamens  are  at  one  level 
and  the  stigmas  at  a  different  level  in  the 

Fig.  203.— Di-  ,  .,      .  ... 

niorphic     flower     same  flower,  while  m  other  mdividuals  of 

(Primula).  '      . 

the  same  species  they  occupy  the  reverse 
positions.  An  insect  visiting  the  flowers  of  the  first 
plant,  becomes  pollinated  at  a  definite  part  of  its  body 
which  does  not  come  into  contact  with  the  stigma  at 
all  in  that  same  type  of  flower.  When,  however,  it 
visits  the  other  type  of  flower,  the  stigma  is  at  tlie 
level  of  the  stamens  of  the  first  type,  and  it  comes  in 


324  SOME  SPECIAL  ADAPTATIONS 

contact  with  the  pollen-bearing  portion  of  the  insect's 
body.  It  has  been  shown  that  even  artificial  pollination 
of  flowers  of  these  species  with  pollen  from  the  same  type 
of  flower  is  unfavorable  to  seed  production,  this  occurring 
best  when  the  pollen  comes  from  the  other  type. 

590.  A  few  plants  (e.g.  the  common  Dandelion,  and 
some  of  the  Hawkweeds)  whose  structures  would  indi- 
cate entomophily,  and  whose  near  relatives  are  so  polli- 
nated, seem  to  have  dropped  the  habit  of  requiring  polH- 
nation,  and  the  eggs  develop  without  fertilization.  Thus 
we  find  a  loss  of  sexuality  in  these  plants  (apogamy, 
parthenogenesis) . 

591.  In  their  methods  of  seed  distribution  also,  the 
Flowering  Plants  show  great  variation.  Some  seeds  are 
let  fall  directly  from  the  parent  plant,  and  are  of  such 
structure  that  they  are  not  suited  to  any  special  means  of 
distribution.  The  result  is  a  crowding  of  the  young  seed- 
lings, and  competition  between  them  and  with  the  parent 
plant.  Such  plants  do  not  extend  their  range  rapidly. 
On  the  other  hand  a  great  proportion  of  the  Flowering 
Plants  have  structures,  either  of  the  parent  plant  or  of 

the  seed,  that  fit  the  seeds  for  special 
modes  of  distribution.  Depending 
upon  the  habitat,  and  means  of 
seed  distribution  the  spread  of  such 
plants  may  be  more  or  less  rapid. 

592.  The  chief  agents  in  seed 
distribution  are  (1)  water,  (2) 
^''''  ^athTcoiSebur.^^'^^''''  ^iud,  (3)  auimals  (including  man), 
and  (4)  mechanical  expulsion. 
Adapted  to  distribution  by  water  are  seeds  (or  fruits) 
with  an  abundance  of  corky  or  woody  tissue  which 
buoys  up  the  seed,  and,  in  the  case  of  ocean-borne 
forms  (e.g.  coconut),  protects  the  seed  from  mechanical 


SEED  DISTRIBUTION  325 

injury  by  the  pouncliiig  of  the  surf.  The  abundant 
springing  up  of  many  kinds  of  weeds  (great  ragweed, 
etc.),  on  flooded  lands  after  the  water  has  subsided 
is  due  to  water-borne  seeds.  Many  of  the  seeds  so 
transported  are  the  small  rounded  seeds  that  are  washed 
along  in  the  mud  (not  floating).  Structures  that  enable 
the  wind  to  transport  seeds  are  almost  innumerable. 
Chief  among  them  are  the  long  hairs  on  seeds  and  fruits 
(thistle,  milkweed,  cottonwood);  flattened  extensions 
into  wings,  which  may  be  more  or  less  spirally  warped 
(elm,  maple,  ash,  catalpa) ;  the  inflorescence  (tickle  grass, 
sycamore),  or  the  whole  plant  (Russian  thistle,  and  other 
'*  tumbleweeds"),  both  rolled  over  the  ground  in  the  wind, 
dropping  the  seeds  as  they  go. 

593.  Distribution  by  animals  is  accomplished  in  many 
ways.  Some  seeds  and  fruits  are  provided  with  hooks  or 
prickles  which  become  caught  in  the  hairs  of  the  passing 


<5) 

Fig.  205. — Spanish  needles,  cherry,  acorn.  Fia.  206. — Touch-me-not. 

animal  and  so  provide  for  the  carrying  of  the  seed  (e.g. 
cocklebur,  sand-bur,  stickseed,  Spanish  needles,  ])ed- 
straw,  burdock,  etc.).  Other  seeds  are  edible  and  so  are 
sought  by  various  animals  which  eat  many  but  drop  some 
in  transporting  them,  or  bury  them  for  future  consump- 
tion, thus  planting  them  (e.g.  acorns,  achenes  of  sun- 
flowers, nuts,  etc.).  Probably  the  development  of  fleshy 
fruits,  however,  is  the  one  that  most  perfectly  provides 
for  seed  distribution.  Animals  of  all  kinds  gather  and 
eat  the  fruits,  and  in  doing  so  drop  the  sclerenchyma- 
enclosed  seeds  (plums,  cherries,  etc.),  or  eat  the  fruits 


326  SOME  SPECIAL  ADAPTATIONS 

with  the  seeds,  the  latter  passing  through  the  body  un- 
harmed (strawberries,  grapes,  and  most  berries).  Many- 
small,  rounded  seeds  dropping  to  the  earth  are  widely 
distributed  by  animals  to  whose  feet  the  earth  containing 
them  clings,  thus  being  carried  long  distances.  Such  are 
the  majority  of  the  common  weeds  of  the  roadsides, 
barnyards,  and  waste  places  (pigweeds,  lamb 's  quarters, 
purslane,  knot-grass,  etc.).  Of  special  interest,  but  rela- 
tively infrequent,  are  the  plants  that  have  fruits  that 
dehisce  explosively  so  that  their  seeds  are  flung  compara- 
tively long  distances,  thus  placing  them  where  they  do 
not  compete  with  their  parents  (OxaHs,  touch-me-not, 
various  vetches,  wild  geranium,  etc.). 

REFERENCE  BOOKS 

W.  F.  Ganong,  The  Living  Plant,  New  York,  1913. 

F.  E.  Clements,  Plant  Physiology  and  Ecology,  New  York, 

1907. 
H.  C.  CowLES,  Ecology  (in  Textbook  of  Botany  by  Coulter, 

Barnes  and  Cowles)  Chicago,  1911. 
Hermann  Muller,  The  Fertilization  of  Flowers,  Engl.  Ed., 

London,  1883. 
Paul   Knuth,    Handbook    of  Flower  Pollination,   Engl.   Ed. 

Oxford,  1906-9. 
Eng.  Warming,  Oecology  of  Plants,  Engl.  Ed.,  Oxford,  1909. 


CHAPTER  XXII 
THE  PLANT  PHYLA 

WITH   THEIR   CLASSES,   ORDERS,   FAMILIES   AND   IL- 
LUSTRATIVE GENERA 

The  Plant  World  is  here  regarded  as  readily  separable  into 
fourteen  Phyla  (often  called  ''Branches"  or  "Divisions"). 
These  are  subdivided  into  Classes,  and  these  again  into  Orders, 
and  the  latter  into  Families.  The  latest  enumeration  of  the 
species  of  plants  shows  that  we  now  know  approximately  a 
quarter  of  a  milUon  recognizable  forms.  These  numerical  data 
may  be  shown  concisely  in  tabular  form  as  follows: 


Classes    Orders    Families        Species 


1.  Myxophyceac  .  . 

2.  Chlorophyceae.. 

3.  Zygophyceae  . . . 

4.  Siphonophyceae 

5.  Phaeophyceae.  . 

6.  Rhodophyceae  . 

7.  Carpomj'ceteae. 

8.  Bryophyta 

9.  Pterido])hyta. . . 

10.  Calamoi)hyta.. . 

11.  Lepidophyta. . .. 

12.  Cycadophyta. . . 

13.  Strobilophyta... 

14.  Anthophyta. . . . 


Total 


2 

4 

16 

2 

7 

16 

2 

4 

21 

3 

9 

26 

3 

5 

24 

2 

7 

24 

3 

29 

145 

2 

7 

65 

2 

5 

13 

3 

3 

4 

2 

3 

7 

4 

6 

13 

1 

2 

9 

2 

32 

300 

33 


123 


About 

2,020 

About 

1,090 

About 

7,000 

About 

1,26a 

About 

1,030 

About 

3,050 

About  64,000 

About  16,600 

About 

3,800 

About 

24 

About 

700 

About 

140 

About 

400 

About  132,500 


683       About  233,614 


327 


328  THE  PLANT  PHYLA 

KEY  TO  THE  PHYLA  OF  PLANTS 

In  this  key  onl}'  the  general  or  typical  characters  are  indi- 
cated, and  it  must  be  reincml)ered  that  many  variations 
("exceptions")  occur  in  every  phylum. 

A.  Cells  typically  with  poorly  developed  nuclei  and  chromato- 

phores;   reproducing   by   fission   and    spores; 
mostly  blue-green,  brown-green  or  fuliginous 
(or  colorless),  never  chlorophyll  green. 
L  Unicellular  to  filamentous  plants. 

Phylum  1.  IMi'xoPHYCEAE. 

B.  Cells  typically  with  well-developed  nuclei  and  chromato- 

phores  (chloroplasts) ;  reproducing  by  fission 
and  spores,  and  mostly  by  gametes  also; 
chlorophyll-green,  sometimes  hidden  by  other 
coloring  matter  (or  colorless). 
L  Plants  usually  of  but  one  obvious  generation,  typi- 
cally aquatic. 

a.  The  fertilized  egg  developing  into  a  z3'gote  only. 

1.  Unicellular,  to  filamentous,  manj^-celled  plants 

(rarely  a  plate  of  cells);  isogamic  to  hetero- 
gamic,  one  or  both  gametes  ciliated. 

Phylum  2.     Chlorophyceae. 

2.  Filamentous  many-celled  plants,  mostly  break- 

ing up  early  into  single  cells;  isogamic,  gam- 
etes not  ciliated.  Phylum  3.  Zygophyceae. 

3.  Tubular  filamentous  (or  saccate)  coenocytic 

plants,  usually  attached  basally  by  rhizoids; 
isogamic  to  heterogamic. 

Phylum  4.     Siphonophyceae. 

4.  Cellular   filamentous    (rarely    unicellular)    to 

massive  plants,  attached  basally  b}^  rhizoids 
(or   roots);    isogamic    to    heterogamic;    the 
green  color  hidden  by  a  brownish  pigment. 
Phylum  5.     Phaeophyceae. 

b.  The  fertilized  egg  developing  into  a  spore-fruit. 

L  Cellular  filamentous  to  massive  holophytic 
plants,  attached  basally  by  rhizoids  (or 
roots);  heterogamic;  the  green  color  mostly 
hidden  by  a  red  or  j)urple  pigment. 

Phvlum  6.     Rhodophyceae. 


KEY  TO  THE  PH\XA  329 

2.  Cellular  filaiiieiitous  hystcrophytic  plants, 
often  much  tlep;enerated,  without  chloro- 
phyll; heterof2;aMiic. 

Phylum  7.     Carpomyceteae. 
II.  Plants  of  two  obvious,  alternating  generations,  tyj)- 
ically  terrestrial. 

a.  Gametophyte  generation  larger,  and  longer-lived 

than  the  dependent  sporophj^te  generation. 
1.  Gametophytes  from  prostrate  and  thalloid  to 
erect  leafy  shoots;  sporophytes  globose  to 
cylindrical  or  stalked,  neither  expanded  nor 
rooted. 

Phylum  8.     Bryophyta. 

b.  Gametophj^te    generation    smaller    and    shorter- 

lived    than    the    independent    sporophyte 
generation. 

1.  Both  generations  mostly  holophytic,  independ- 

ent of  one  another. 

(a)  Gametophytes  typically  flat  and  thal- 
loid, normally  attached  by  rhizoids, 
mostly  monoecious;  sporophytes  consist- 
ing of  large-leaved,  solid  stems,  which 
are  rooted  below. 

Phylum  9.     Pteridophyta. 

(b)  Gametophytes  typically  fiat  and  thal- 
loid, normall}^  attached  by  rhizoids, 
mostly  monoecious;  sporophytes  con- 
sisting of  mostly  solid,  cylindrical, 
jointed  and  fluted  stems,  bearing  small, 
whorled  leaves  at  the  nodes,  and  rooted 
below.         Phylum  10.     Calamophyta. 

(c)  Gametophytes  typically  tubular  or  glo- 
bose, with  few  rhizoids  or  none,  often 
dioecious;  sporophytes  consisting  of 
solid,  cylindrical,  continuous  (not  joint- 
ed) and  not  fluted  stems,  bearing  small 
spirally  arranged  (or  opposite)  leaves, 
and  rooted  l)elow. 

Phylum  11.     Lepidopiiyta. 

2.  Gametophytes  hystcrophytic,  dependent  upon 

and  nourished  by  the  8j)oroi)hyto. 


330  THE  PLANT  PHYLA 

(a)  Sporophylls    open,    ovules    and    seeds 
naked  (gymnospermous). 

(1)  Gametophytes  dioecious;  sperms  cili- 
ated and  motile;  sporophytes  pro- 
ducing microspores  and  megaspores 
in  spiral  or  whorled  sporophylls,  or 
these  aggregated  into  cones. 

Phylum  12.     Cycadophyta. 

(2)  Gametophytes  dioecious;  sperms  not 
ciliated,  not  motile;  sporophytes 
with  sporophylls  in  cones. 

Phylum  13.    Strobilophyta. 

(b)  Sporophylls    closed,    ovules    and    seeds 

covered  (angiospermous). 
(1)  Gametophytes  dioecious;  sperms  not 
ciliated,    not    motile;    sporophytes 
with  sporophylls  in  flowers. 

Phylum  14.    Anthophyta. 

In  the  following  systematic  enumeration  many  of  the  families 
are  merely  named  in  their  sequence,  without  any  characteriza- 
tion or  examples.  Moreover  the  characterizations  of  all  groups 
are  necessarily  very  brief  and  general.  The  examples  cited  are 
of  the  more  conmion  genera,  or  those  of  particular  interest  to 
the  student. 

Phylum  I.     MYXOPHYCEAE.     The  Slime  Algae 

Usually  blue-green,  poorly  developed  cells,  or  filaments 

Class    1.      ARCHIPLASTIDEAE    (Cyanophyceae).      "Blue 
Greens."     Without     nuclear     mem- 
brane.    (Sp.  about  2,000.) 
Order  Coccogonales.     Green  or  greenish;  unicellular. 
Family    1.  Chroococcaceae.     Cells  rounded. — Chroo- 

coccus,  Gloeocapsa,  IMerismopedia. 
Family    2.  Chamaesiphonaceae.     Cells   elongated. — 
Chamaesiphon. 
Order  Hormogonales.     Mostly  green  or  greenish;  fila- 
mentous. 
Family    3.  Oscillatoriaceae.     No  heterocysts. — Oscil- 
lator ia,  Lyngbya. 


MYXOPHYCEAE  331 

Family  4.  Nostocaceae.  Heterocysts  intercalary 
prominent. — N  ostoc,  Cylindrosper 
mum. 

Family  5.  Scytonemataceae.  Heterocysts  intercal- 
ary, not  prominent. — Scytonema. 

Family  (J.  Rivulariaceae.  Heterocysts  basal. — Rivu- 
laria. 

Family  7.  Camptotrichaceae.  Xo  heterocysts. — 
Camptothrix. 

Family  8.  Stigonemataceae.  Heterocysts  intercal- 
ary, not  prominent;  cells  in  more  than 
one  row. — Stigonema. 
Order  Bacteriales.  The  Bacteria.  Not  green;  typically 
filamentous,  but  becoming  few-  or 
one-celled  by  the  solution  of  the  fila- 
ment. Related  to  the  foregoing  blue- 
green  plants. 
Sub-order  Thiobacteria.  With  sulphur  granules  in  the 
cells. 

Family  9.  Beggiatoaceae.  Cells  in  motile  filaments, 
colorless. — Beggiatoa. 

Family  10.  Rhodobacteriaceae.     Cells    single,   or    in 
colonies;  red,  rose  or  violet  colored. — 
Chromatium. 
Sub-order  Eubacteria.     Without  sulphur  granules  in  the 
cells. 

Family  11.  Phycobacteriaceae.  Cells  in  straight, 
motionless  filaments. — C renothrix, 
Sphaerotilus. 

Family  12.  Spirillaceae.  Cells  in  spirally  coiled,  mo- 
tile filaments. — Spirillum,  ]\licrospira, 
Spirochaete. 

Family  13.  Bacteriaceae.  Cells  mostly  single,  elon- 
gated, straight. — Bacterium  (no  flag- 
ella),  Bacillus  (surface  flagella), 
Pseudomonas  (polar  flagella). 

Family  14.  ]\Iyxobacteriaceae.  Cells  elongated,  with- 
out flagella,  growing  in  definite,  slimy 
colonies. — Chondromyces. 

Family  15.  Coccaceae.  Cells  mostly  single,  spherical. 
— Micrococcus,  Streptococcus,  Sar- 
cina. 


332  THE  PLANT  PHYLA 

Class    2.     HOLOPLASTIDEAE.     With  nuclear    menihrane. 
(Sp.  about  20.) 
Order  Glaucocystales.     Dividing  in  one  plane. 
Family  16.     Glaucocystaceae. — Glaucocystis. 

Phylum  II.     CHLOROPHYCEAE.     Tlie  Simple  Algae 

Normally  chloro])liyll-green,  with  well-developed  single  cells, 
or  filaments.  (Here  restricted  to  two 
classes  of  green  algae). 

Class  3.     PROTOCOCCOIDEAE.     Green  Slimes.     Unicellu- 
lar.    (Sp.  about  450.) 
Order  Palmellales.     Cells  not  in  colonies. 

Family  1.  Protococcaceae.     No     zoospores. — Proto- 

coccus,  Trochiscia,  Crucigenia. 
Family  2.  Chlorococcaceae.  With  zoospores. — Chloro- 

coccum,  Tetraspora.  Botryococcus. 
Family  3.    Synchytriaceae.     Colorless  parasites. — 
Olpidium,  Synchytrium. 
Order  Coenobiales.     Cells  in  colonies. 

Family    4.  Hydrodictyaceae.  Vegetative  cells  not  cili- 
ated.— Scenedesmus,  Hydrodictyon. 
Family    5.  Volvocaceae.     Vegetative  cells  ciliated. — 
Gonium,   Pandorina,   Volvox.     (Ani- 
mals!) 
Class  4.     CONFERVOIDEAE.     Confervas.     Filamentous, or 
a  plane.     (Sp.  about  640.) 
Order  Microsporales.     Unbranched. 

Family    6.  Microsporaceae. — Microspora. 
Order  Schizogoniales.     Unbranched. 

Family    7.  Prasiolaceae. — Prasiola. 
Order  Ulvales.     Plant  a  plane  or  tube. 

Family    8.  Ulvaceae. — Ulva,  Enteromorpha. 
Order  Chaetophorales.     Usually  branched.     Zoospores 
and  ciliated  gametes. 
Family    9.  Ulotrichaceae.     Unbranched. — Ulothrix. 
Family  10.  Chaetophoraceae.     Branches  attenuated 
into     hairs. — Draparnaldia,    Chaeto- 
phora. 
Family  11.  Alicrothamniaceae.     Scarcely  attenuated, 
no  hairs. — Microthamnion. 


ZYGOPHYCKAE  333 

Family  12.  Trent epohliaceae.     Scarcely    attenuated, 

no  hairs. — Trent cpohlia. 
Family  13.  Herposteiraceac.     Scarcely      attenuated, 

with  hairs. — Herposteiron. 
Family  14.  Cylindrocapsaceae.     Unbranchcd,  hetero- 

gamic. — Cylindrocapsa. 
Family  15.  Oedogoniaceao.   Unbranched  or  branched, 

heterogamic. — Oedogonium. 
Order  Coleochaetales.     Branched,  fusing  into  discs. 
Family  16.  Coleochaetaceae.     Minute    disk-like 

plants. — Coleochaete. 


Phylum  III.     ZYGOPHYCEAE.     The  Conjugate  Algae 

Chlorophyll-green  sluggish  filaments,  often  fragmenting  into 
single  cells 

Class  5.      CONJUGATAE.     Typically     filamentous,    green 
plants,    with    cellulose    walls.     (Sp. 
about  1,300.) 
Order  Zygnematales.     Pond  Scums.     Filamentous. 

Family    1.  Mesocarpaceae.     Chloroplast  single,  long, 

axial. — Mougeotia,  Gonatonema. 
Family    2.  Zygnemataceae.     Chloroplasts  two,  short, 

axial. — Zygnema,  Zygogonium. 
Family    3.  SpirogjTaceae.     Chloroplasts  1  to  9,  parie- 
tal, spiral. — Spirogyra. 
Order  Desmidiales.     Desmids.     Filaments  usually  early 
fragmenting  into  single  cells. 
Family    4.  Desmidiaceae.     Unbranched  filaments. — 
Genicularia,  Hyalotheca,  Desmidium. 
Family    5.  Closteriaceae.     Cells  solitary,  elongated. 

— Clostcrium,  Pcnium. 
Family    G.  Cosmariaceae.     Cells  solitary,  broad,  flat- 
tened.— Cosmarium,  ^licrastcrias. 
Class   6.     BACILLARIOIDEAE.     The  Diatoms.     Brownish- 
green    plants,    with    silicified    walls. 
(Sp.  about  5,700.) 
Order  Eupodiscales.     Round  Diatoms.     Filaments  com- 
monly cylindrical,  usually  fragmented 
into  single  cells. 


334  THE  PLANT  PHYLA 

Family  7.  Coscinodiscaceae.  Cells  short,  ends  not 
ribbed. — Coscinodiscus. 

Family  8.  Actinodiscaceae.  Cells  short,  ends  rib- 
bed.— Actinodiscus,  Arachnoidiscus. 

Family  9.  Eupodiscaceae.  Cells  short,  ends  with 
"eves." — Eupodiscus,  Actinocyclus. 

Family  10.  Soleniaceac;    11,    Chaetocerotaceae;    12, 
Biddulphiaceae;  13,  Euodiaceae;   14, 
Anauliaceae;  15,  Rutilariaceae. 
Order  Naviculales.    Flat  Diatoms.    Filaments  flattened, 
usually  fragmented  into  single  cells. 

Family  16.  Tabellariaceae.  Mostly  filaments,  cells 
short,  rectangular  in  side  view. — 
Grammatophora,  Rhabdonema. 

Family  17.  Meridionaceae;  18,  Fragilariaceae. 

Family  19.  Naviculaceae.  Cells  single,  end  with 
central  slit. — Navicula,  Amphipleura. 

Family  20.  Bacillariaceae;  21,  Surirellaceae. 

Phylum  R'.     SIPHONOPHYCEAE.     The  Tube  Algae 

Normally  chlorophyll-green  filaments  composed  of  one  or  more 
coenocytes 

Class   7.     VAUCHERIOIDEAE.    Lower  Tube  Algae.     Fila- 
ments septate  or  tubular.     (Sp.  about 

400.) 
Order  Cladophorales.     The  Cladophoras.     Septate,  the 

segments  coenocytic. 
Family    1.  Cladophoraceae.    Unbranched  or  branched, 

isogamic. — Cladophora,  Pithophora. 
Family    2.  Sphaeropleaceae.    Unbranched,  hetero- 

gamic.     Sphaeroplea. 
Order  Siphonales.     Green   Felts.     Tubular,   irregularly 

branched,  chlorophyllose. 
Family    3.  Phyllosiphonaceae.     Endophytic. — Phyl- 

losiphon. 
Family    4.  Codiaceae.     Filaments  compacted  into  a 

large     plant-body. — Codium,     Peni- 

cillus. 
Family    5.  Vaucheriaceae*     Filaments  single,  free. — 

Vaucheria. 


SIPHONOPIIYCEAE  335 

Class  8.  PHYCOMYCETEAE.  Tube  Fungi.  Lower  Fungi. 
Filaments  tubular,  mostl}-  irregularly 
branched,  chlorophyll-less.  (About 
400  species.) 
Order  Saprolegniajles.  Typically  aquatic;  mostly  sapro- 
phytic ;  forming  zoospores  in  zoospor- 
angia. 

Family  6.  IVIonoblepharidaceae.  Aquatic  sapro- 
phytes; antherids  producing  unicili- 
ated  sperms. — Monoblepharis. 

Family  7.  Saprolegniaceae.  Water  Molds.  Aquatic, 
parasitic  or  saprophytic;  antherids 
not  producing  sperms. — Saprolegnia, 
Achlya. 

Family    8.  Pythiaceae;  9,  Cladochytriaceae;  10,  An- 
cylistaceae. 
Order  Peroxosporales.     Non-aquatic;  mostly  parasitic 
in  the  tissues  of  higher  plants;  usually 
forming  zoospores  in  conidia. 

Family  11.  Albuginaceae.  White  Rusts.  Conidia  in 
chains. — Albugo. 

Family  12.  Peronosporaceae,  Downy  Mildews. 
Conidia  terminal  singly  on  branched 
conidiophores. — Phytophthora,  Plas- 
mopara,  Peronospora. 
Order  Mucorales.  Typically  non-aquatic;  saprophytic, 
or  parasitic  on  other  fungi;  not  form- 
ing zoospores;  spores  single,  clustered, 
or  in  sporangia. 

Family  13.  Mucoraceae,  Black  Molds.  Sporangium 
with  a  columella. — Rhizopus,  Mucor, 
Pilobolus. 

Family  14.  IMortierellaceae.  Sporangium  without  a 
columella. — Mortierella. 

Family  15.  Chaetocladiaceae.  Spores  single,  or  clus- 
tered on  branched  conidiophores. — 
Chaetocladium. 

Family  16.  Piptocephalidaceae.  Spores  in  chains, 
clustered  on  the  ends  of  branches. — 
Piptocephalis,  Synccphalis. 


336  THE  PLANT  PH\TA 

Order  Entomophthorales.     Xon-aquatic;  mostly  para- 
sitic in  insects;  without  zoospores. 

Family  17.  Entomophthoraccae.  Fly  Fungi. — Ento- 
mophthora. 
Class  9.  BRYOPSIDOIDEAE.  Higher  Tube  Algae.  Globu- 
lar to  stipitate  or  dendroid,  septate  or 
continuous.  (Sp.  about  4G0.) 
Order  Valoniales.  Globular  coenocytes  to  compound 
septate  plants.     Isogamic. 

Family  18.  Botrydiaceae.  Little  Bladder  Algae. 
Minute,  globular,  terrestrial  green 
plants. — Botrydium,  Protosiphon. 

Family  19.  Chytridiaceae.  Minute,  globular,  endo- 
phytic, colorless  plants. — Chytri- 
dium. 

Family  20.  Valoniaceae.  Large  Bladder  Algae.  Large, 
usually    septate,     marine     plants. — 
Valonia,     Struvea,     Halicystis. 
Order  Dasycladales.    Regularly  branched,  non-septate, 
marine  plants.     IMostly  isogamic. 

Family  21.  Derbesiaceae. 

Family  22.  Bryopsidaceae.  Sea  Ferns.  Dendroid, 
erect,  pinnately  branched. — Bryopsis. 

Family  23.  Caulerpaceae. 

Family  24.  Dasycladaceae.  Erect  with  whorled 
branches. — Dasycladus,  Acetabularia. 
Order  Charales.  The  Stoneworts.  Erect,  rooted,  sep- 
tate, dendroid,  with  whorled  branches, 
heterogamic,  antherids  compound. 
(Sp.  about  160.) 

Family  25.  Nitellaceae.  Oogone  crown  of  ten  cells. — 
Nitella,  Tolypella. 

Family  26.  Characeae.  Oogone  crown  of  five  cells. — 
Chara,  Lamprothamnus. 

Phylum  V.    PHAEOPHYCEAE.     The  Brown  Algae 

Brown-green  filamentous  to  large,  massive  plants,  marine 

Class  10.  PHAEOSPOREAE.  Kelps.  Reproductive  organs 
external,  isogamic  to  heterogamic. 
(Sp.  about  550.) 


PHAEOPHYCEAE  SAT 

Order  Ectocarpales.     Zoospores  and  isogametes  similar 
and  motile. 

Family  1.  Ectocarpaceae.  Mostly  filamentous,  sim- 
ple or  branched,  with  zoosj)ores  and 
gametes. — Ectocarpus,  Streblonema. 

Family  2.  Myriotrichiaceae;3,  Choristocarpaceae;  4, 
Elachistaceae;  5,  Chordariaceae;  6, 
Stilophoraceae;  7,  Spermatochnaceae; 
8,  Sporochnaceae;  9,  Encoeliaceae;  10, 
Desmarestiaceae;  11,  Arthrocladia- 
ceae;  12,  Sphacelariaceae;  13,  Ralf- 
siaceae;  14,  Striariaceae;  15,  Dictyo- 
siphonaceae. 

Family  16.  Laminariaceae.  Large,  parenchymatoas, 
usually  stalked,  with  zoospores  only. 
— Laminaria,  Alaria,  Postelsia,  Nereo- 
cj'stis,  Macrocj'stis.  Egregia. 
Order  Cutleriales.  Zoospores  and  heterogametes  dis- 
similar and  motile. 

Famil}^  17.  Cutleriaceae;  18,  Splachnidiaceae. 
Order  Tilopteridales.   Zoospores  and  heterogametes  dis- 
similar, eggs  non-motile. 

Family  19.  Tilopteridaceae. 
Class  11.  DICTYOTINEAE.     Reproductive  organs  external, 
heterogamic.     (Sp.  about  130.) 
Order  Dictyotales.     Plants  erect,  flat,  leaf-like. 

Family  20.  Dictyotaceae. — Dictyota,  Padina,  Zonaria. 
Class  12.  CYCLOSPOREAE.     Rockweeds.     Reproductive  or- 
gans in  sunken  conceptacles,  hetero- 
gamic.    (Sp.  about  350.) 
Order  Fucales.     Usually  flattish,  branched. 

Family  21.  Durvillaeaceae.  Conceptacles  on  vegetative 
])arts  of  plant. — Durvillaea. 

Family  22.  Himanthaliaceae.  Conceptacles  on  long 
branches  arising  from  a  vegetative 
cup. — Himanthalia. 

Family  23.  Fucaceae.  Conceptacles  on  ends  of  vegeta- 
tive branches. — Fucus.  Ascophyllum. 

Family  24.  Sargassaceao.  Conceptacles  on  small 
lateral  branches. — Sargassum,  Ilali- 
drys. 

22 


338  THE  PLANT  PHYLA 

Phylum  Vl.    RHODOPHYCEAE.     The  Red  Algae 

Red  to  purple  filamentous  to  massive  plants;  marine 

Class  13.  BAXOIOIDEAE.  Antherids  and  oogones  developed 
from  ordinary  cells  of  plant  body; 
propagation  by  monospores.  Red  or 
purple  ])lants.  (Sp.  about  50,  doubt- 
fully belonging  here.) 
Order  Bangiales.     One  chloroplast  in  each  cell. 

Family    1.  Bangiaceae.      Including    the   genus  Por- 
phyra. 
Order    Rhodochaetales.  Several  to  many   chloroplasts 
in  each  cell. 
Family    2.  Rhodochaetaceae;  3,  Campsopogonaceae. 
Class  14.  FLORIDEAE.     Red    Seaweeds.     Antherids    and 
oogones  specially  developed;  propaga- 
tion by  tetraspores.     Red  or  purple 
plants.     (Sp.  about  3,000.) 
Order  Nemalionales.      Lower  Red  Seaweeds.      Mostly 
filamentous  plants.    Sporophores  pro- 
duced  directly   from  fertilized  eggs. 
Family    4.  Lemaneaceae. 

Family    5.  Helminthocladiaceae.        Filamentous    or 
parenchymatous,  variously  branched. 
— Batrachospermum,  Nemahon. 
Family    6.  Thoreaceae;    7,  Chaetangiaceae;  8,  Geli- 
diaceae. 
Order  Cryptonemiales.    Hard  Red  Seaweeds.    Filiform, 
branched,    often   complanate;   sporo- 
phores produced  by  remote  auxiliary 
cells. 
Family    9.  Gloiosiphoniaceae;    10,    Grateloupiaceae; 
11,    Dumontiaceae;     12,     Nemasto- 
maceae;    13,    RhiziphyUidaceae;    14, 
Squamariaceae. 
Family  15.  Corallinaceae.        Filamentous,  branched 
(and  jointed)  to  crustaceous. — Coral- 
lina. 
Order  Ceramiales.  "Sea    Mosses."     Fihform    to    folia- 
ceous  plants.    Sporophores  produced 
by  nearby  auxiliary  cells. 


RHODOPHYCEAE  339 

ramily  1(3.  Dclessaricceac.  Foliaceous. — Delesseria, 
Grinnellia,  Nitophylluni. 

Family  17.  Bonnemaisoniaceae. 

Family  18.  Rhodomelaceac.  Cylindrical,  flattened, 
to  foliaceous. — Poly.siplionia,  Rhodo- 
mela,  Dasya. 

Family  19.  Ceramiaceae.  Filiform,  branched,  com- 
planate. — Ceramium,  Lcjolisia,  Pti- 
lota. 
Order  Gigartinales.  Soft  Red  Seaweeds.  Parenchyma- 
tous plants;  sporophores  produced  by 
the  nearby  auxiliary  cells  branching 
in  the  tissues. 

Family  20.  Acrotylaceae. 

Family  21.  Gigartinaceae.  Erect  or  spreading,  branch- 
ing, cylindrical  to  flat  plants.  Chon- 
drus,  Gigartina,  Callophyllis. 

Family  22.  Rhodophyllidaceae.  Erect,  or  spreading 
branching,  flat  plants. — Rhodophyllis 
Rhabdonema. 
Order  Rhodyaieniales.  Higher  Red  Seaweeds.  Filiform, 
to  foliaceous  and  massive  plants; 
sporophores  produced  b}'  nearby  aux- 
iliary cells  growing  outward  in  plant 
body. 

Family  23.  Sphaerococcaceae. 

Family  24.  Rhodymeniaceae.  Filiform  to  foliaceous. 
Rhodymenia,  Plocamium. 

Phylum  VII.  CARPOMYCETEAE.     The  Higher  Fungi 
Terrestrial,  chlorophyll-less,  filamentous,  parasites  and  sapro- 
phytes, producing  spore-fruits 
Class  15.  ASCOSPOREAE.     Ascus  Fungi.     Spore-fruits  con- 
taining one  or  more  asci  with  asco- 
spores.     (Sp.  about  29,000.) 
Order  Laboulbeniales.     Beetle  Fungi.     Erect,  minute, 
few  celled,  bearing  simple  ascigerous 
fruits. 
Family      1.  Laboulbeniaceae.  Parasitic  on  beetles. — 
Laboulbcnia,     Ceratomyces,     Dicho- 
myces. 


340 


THE  PLANT  PHTiXA 


Order  Discolichenes.  Disk  Lichens.  Lichen-forming 
fungi  with  asci  in  apothecia. 

Famil}^  2.  Lecanactidaceae;  3,  Pilocarpaceae;  4, 
Chrysothricaceae;  5,  Thelotrema- 
taceae;  6,  Diploschistaceae;  7,  Ecto- 
lechiaceae;  8,  G^-alectaceae;  9,  Coe- 
nogoniaccae;  10,  Lecidiaceae;  11, 
Phyllopsoraceae. 

Family  12.  Cladoniaceae.  Crustaceous  to  scaly  or 
foliose,  with  Protococcus  hosts 
(rarely  Myxophyceae  hosts). — Beo- 
myces,  Cladonia,  Stereocaulon. 

Family  13.  Gyrophoraceae.  Foliose,  coriaceous,  with 
Protococcus   hosts. — Umbilicaria. 

Family  14.  Acarosporaceae.  Crustaceous,  scaly  or 
foliose,  with  Protococcus  hosts — The- 
locarpon,  Acarospora. 

Family  15.  Ephebaceae;  16,  Pyrenopsidaceae;  17, 
Lichinaceae. 

18.  Collemataceae.  Gelatinous  to  crusta- 
ceous, scaly  foliose  to  fruticose,  with 
Nostoc  hosts. — Physma,  Collema, 
Leptogium. 

19.  Heppiaceae;  20,  Pannariaceae. 
21.  Stictaceae.     Fohose,    with   Palmella   or 

Nostoc  hosts. — Sticta,  Lobaria. 

Family  22.  Peltigeraceae.  Foliose  with  Palmella  or 
Nostoc  hosts. — Peltigera. 

Family  23.  Pertusariaceae.  Crustaceous,  with  Pro- 
tococcus hosts. — Pertusaria. 

Family  24.  Lecanoraceae.  Crustaceous,  with  Pro- 
tococcus hosts. — Lecanora. 

Family  25.  Parmeliaceae.  Foliose,  with  Protococ- 
cus hosts. — Parmelia. 

Family  2G.  Usneaceae.  Fruticose,  with  Protococcus 
hosts. — Usnea,  Ramalina. 

Family  27.  Caloplaceae.  Crustaceous,  with  Proto- 
coccus hosts. — Caloplaca. 

Family  28. — Theloschistaceae.  Foliose  to  fruticose, 
with  Protococcus  hosts. — Thelo- 
schistes. 


Family 


Family 
Family 


CARPOMYCETEAE  341 

Family    29.  Buelliaccae.  Crustaceous,  with  Protococ- 

cus  hosts. — Buellia. 
Family    30.  Physciaceae.    Foliose  to  fruticose,  with 
Protococcus  hosts. — Physcia. 
Order  Caliciales.    Powdery    Lichens.     Common    fungi, 
and   lichen-forming  fungi;  apothecia 
spheroidal,  pulverulent. 
Family    31.  ProtocaHciaceae.      True    fungi,     sapro- 
phytic.— Mycocalicium. 
Family    32.  Caliciaceae.    Crustaceous    Hchens,   with 
Protococcus    or   Stichococcus    hosts. 
• — Calicium. 
Family    33.  Cypheliaceae.  Crustaceous  lichens  with 
Protococcus  or  Trentepohlia  hosts. 
— Cyphelium,  Tylophoron. 
Family    34.  Sphaerophoraceae.    Foliose  or  fruticose 
lichens     with      Protococcus     hosts. — 
Sphaerophorus. 
Order  Phacidiales.     Little  Cup-fungi.     Common  fungi, 
spore-fruits  open  (apothecia). 
Family    35.  Stictidaceae.       Fleshy,  yellow. — Stictis, 

Propolis. 
Family    36.  Tryblidiaceae.     Leathery  or  carbonace- 
ous,   black. — Tryblidium,    Scleroder- 
ris. 
Family    37.  Phacidiaceae.     Leathery    or  carbonace- 
ous, black. — Phacidium,  Rhytisma. 
Order    Exoascales.     Pocket    Fungi.     Common    fungi; 
apothecia   much   reduced   and   sim- 
plified. 
Family    38.  Exoascaceae.     Parasitic  in  higher  plants. 

— Exoascus,  Taphrina. 
Family    39.  Ascocorticiaceae.        Saprophytic,      asci 

forming  a  cushion. — Ascocorticium. 
Family  40.  Endomycetaceac.  Asci  single,  not  in 
masses  or  in  cushions. — Endomyces, 
Ercmascus. 
Order  Pkzizales.  Cup-fungi.  Conmion  fungi;  apothe- 
cia at  length  cup-shaped,  fleshy  or 
leathery. 


342 


THE  PLANT  PHYLA 


Family    41.  Pyronemataceae.     Fleshy,  open  from  the 

first. — Pyronema. 
Family    42.  Pezizaceae.     Fleshy,  first  spherical,  later 

open. — Lachnca,  Peziza. 
Family    43.  Ascobolaceae.     Fleshy,   first    spherical, 

later  open. — Ascobolus. 
Family    44.  Helotiaceae.     Fleshy,  mostly  open  from 

the   first. — Sclerotinia,    Dasyscypha, 

Helotium. 
Family    45.  AloUisiaceae;  46,  Celidiaceae;  47,  Patel- 

lariaceae;  48,  Cenangiaceae;  49,  Cor- 

dieritidaceae;  50,  Cyttariaceae. 
Order  Helvellales.     Helvellas.     Common   fungi;  apo- 

thecia  open  from  the  first;  fleshy  or 

gelatinous. 
Family    51.  Rhizinaceae.     Sessile. — Rhizina. 
Family    52.  Geoglossaceae.  Stalked,    capitate. — ]\Ii- 

trula,  Geoglossum. 
Family    53.  Helvellaceae.    Stalked,  capitate. — Mor- 

chella,  Verpa,  Helvella. 
Order     Graphidales.        SHt     Lichens.     Lichen-forming 

fungi,  aUied  to  the  preceding  families. 
Family    54.  Arthoniaceae.    Crustaceous,   with    Pal- 

mella,  Trentepohlia,  or  Phyllactidium 

hosts. — Arthonia,  Arthothelium. 
Family    55.  Graphidaceae.     Crustaceous,  with  Pal- 

mella  or   Trentepohlia  hosts. — Ope- 

grapha,  Graphis,  Graphina. 
Family    56.  Chiodectonaceae;  57,  Dirinaceae. 
Family    58.  Roccellaceae.  Fruticose,  erect,  with  Tren- 
tepohlia hosts. — Roccella. 
Order  Pyrenolichenes.     Closed  Lichens.     Lichen-form- 
ing  fungi,    aUied    to   the   preceding 

families. 
Family    59.  Moriolaceae.     Crustaceous,  with  Cysto- 

coccus  hosts. — Moriola. 
Family    ()0.    Epigloeaceae.     Gelatinous,    with    Pal- 

mcUa  hosts. — Epigloea. 
Family    6L  Verrucariaceae.     Crustaceous  with  Prot- 

ococcus   or   Palmella    hosts. — Verru- 

caria,  Thelidium. 


CARPOMYCETEAE 


343 


Family 
Family 


Family    62.  Dermatocarpaceae;  63,    Pyrenothamni- 
aceae;  64,    Pyrenulaceae;  65,    Phyl- 
lopyreniaceae;    66,    Trypethcliaceae; 
67,     Paratheliaceae;     68,    Astrothe- 
liaceae;  69,  Strigulaceae;  70,  Pyreni- 
diaceae;  71,  Mycoporaceac. 
Order  Pyrenomycetales.     Closed  Fungi.     Filamentous, 
with  mostly  compound  closed  spore- 
fruits. 
Family    72.  Hypocreaceae.     Mostly  reddish  or  yel- 
lowish.—Nectria,   Cordyceps,   Clavi- 
ceps. 
Family    73.  Dothidiaceae.    Black.— Plowrightia, 
Dothidea,  Phyllachora. 
74.  Sordariaceae;  75,  Chaetomiaceae. 
76.  Sphaeriaceae.     Simple,     superficial     or 
sunken.— Trichosphaeria,  Lasio- 
sphaeria. 
Family    77.  Ceratostomataceae;    78,    Cucurbitaria- 
ceae;    79,     Amphisphaeriaceae;    80, 
Lophiostomataceae;  81,   IMycosphae- 
rellaceae;  82,  Pleosporaceae;  83,  Mas- 
sariaceae;  84,  Gnomoniaceae. 
Family    85.  Valsaceae.     Permanently  enclosed  in  a 
black    stroma.— Valsa,    Anthostoma, 
Diaporthe. 
Family    86.  Melanconidiaceae;  87,  Diatrypaceae;  88, 

Melogrammataceae. 
Family    89.  Xylariaceae.       Peripheral     in    massive 
stroma.— Hypoxylon,  Xylaria. 
Order  Hysteriales.     Slit  Fungi.     Common  fungi;  sapro- 
phytic, apothecia  opening  by  a  slit. 
Family    90.  Hypodermataceae;  91,  Dichaenaceae;  92, 

Ostropaceae. 
Family  93.  Hysteriaceae.    Carbonaceous  or  leathery, 
elongated.— Hysterographium,    Hys- 

terium. 
Family    94.  Acrospcrmaceae. 
Order  Perisporiales.     IVlildews.     Filamentous,  with  sim- 
ple, mostly  spherical  spore-fruits. 


344  THE  PLANT  PHYLA 

Family  95.  Erysiphaceae.  Superficial  parasites  upon 
higher  plants. — Erysiphe,  Micro- 
sphaera,  Uncinula,  Podosphaera. 

Family    96.  Perisporiaceae;  97,  IVIicrothyriaceae. 
Order  Aspergillales.     Little  Tubers.     Common  fungi; 
spore-fruits  minute  or  small,  mostly 
not  subterranean. 

Family  98.  Gymnoascaceae.  Loose  hyphae,  central- 
ly ascigerous. — Gj'mnoascus. 

Family  99.  Aspergillaceae.  Spheroidal,  parenchy- 
matous, sessile. — Aspergillus,  Penicil- 
lium. 

Family  100.  Onj^genaceae;  101,  Trichocomataceae; 
102,  Elaphomycetaceae. 

Family  103.  Terfeziaceae.     Spore-fruits  subterranean 
resembling  small  Tubers. — Terfezia. 
Order  Hemiascales.     Common  fungi;  no  apothecia;  asci 
single,  scattered. 

Family  104.  Ascoideaceae;  105,  Protomycetaceae. 

Family  106.  Saccharomycetaceae.     Yeast  fungi,  asci 
early  isolated. — Saccharomyces. 
Order  TuBERALES.     Tubers.    Common  fungi;  spore-fruits 
large,  tuberous,  subterranean,  fleshy, 
internally  ascigerous. 

Family  107.  Tuberaceae.  Eventually  opening. — 
Tuber. 

Family  108.  Balsamiaceae.  Not  opening. — Balsamia. 
Class  16.  BASIDIOSPOREAE.  Basidium  Fungi.  Spore-fruits 
containing  one  or  more  basidia  with 
basidiospores.  (Sp.  about  14,000.) 
Order  Hymenogastrales.  False  Tubers.  Spore-fruits 
large,  tuberous,  subterranean,  fleshy, 
with  internal  hymenium.  Sapro- 
phytes. 

Family  109.  Hymenogastraceae.  Resembling  Tuber- 
aceae.— Hysterangium,  Hj^menogas- 
ter,  Octaviana,  Rhizopogon. 
Order  Sclerodermatales.  Hard  puff-balls.  Spore- 
fruits  small  to  large,  roundish,  event- 
ually pulverulent.     Saprophytes. 


CARPOMYCETEAE  345 

Family  110.  Scleroderinataceao.  Spore-fruits  round, 
often  stalked. — Scleroderma. 

Family  111.   Podaxaceae.     Spore-fruit    pyriform     or 

clavate,  stalked. — Secotium,  Podaxon. 

Order  Lycopehdales.       Pulf-balls.       Spore-fruits  large, 

fleshy,    at    first    subterranean,    later 

emerging — Saprophytes. 

Family  112.  Lycoperdaceae.  Sessile  or  short^stalked. 
— Lycoperdon,  Bovista,  Geaster. 

Family  1 1.3.  Tylostomataeeae.  Long-stalked. — Tylo- 
stoma,  Battarea. 
Order  Xidulariales.  Bird-nest  Fungi.  Spore-fruits 
small,  spherical  or  top-shaped,  leath- 
ery, containing  one  or  more  peridioles. 
Saprophytes. 

Family  114.  Nidulariaceae.  With  several  peridioles. 
— Nidularia,  Crucibulum,  Cyathus. 

Family  115.  Sphaerobolaceae.  With  but  one  peridiole. 
— Sphaerobolus. 
Order  Phallales.  Stink-Horns.  Spore-fruits  large, 
fleshy,  at  first  tuberous  and  subter- 
ranean, later  stalked  and  emerging. 
Saprophytes. 

Family  116.  Phallaceae.  Stalk  cylindrical,  capped 
with  spore-mass. — Mutinus,  Ithyphal- 
lus,  Dictyophora. 

Family  117.  Clathraceae.  Stalk  ovoid  and  reticu- 
lated, or  branched. — Simblum,  Clatli- 
rus,  Aseroe. 
Order  Ar.ARicALES.  Toadstool  Fungi.  Spore-fruits  large, 
umbrella-shaped,  bracket-shaped  or 
variously  branched;  hymenium  even- 
tually external. — Saprophytes  and 
parasites. 

Family  U.S.  Agaricaceae.  Agarics  or  Toadstools; 
typically  umbrella- shaped,  usually 
fleshy;  hymenium  on  gills. — Cop- 
rinus,  Russula,  Psalliota,  Agaricus, 
Amanita. 

Family  11!).  Polyporaceae.  Polypores:  from  umbrel- 
la-shaped to  bracket-shaped,  fleshy  to 


346  THE  PLANT  PHYLA 

leathery  or  woody;  hymenium  lining 
pits  or  pores. — Boletus,  Polyporus, 
Fomes,  Polystictus. 

Family  120.  Hj'dnaceae.  Prickly  Fungi.  From  um- 
brella-shaped to  bracket- shaped, 
fleshy  to  leathery  or  woody;  hymen- 
ium on  warts  or  prickles. — Hydnum, 
Irpex. 

Famil}^  12L  Clavariaceae.  Coral  Fungi.  Cylindrical 
to  clavate  and  fruticose,  mostly 
leathery;  hymenium  superficial. — Pis- 
tillaria,  Clavaria. 

Family  122.  Thelephoraceae.  Leathery  Fungi.  Flat, 
shell-shaped,  capitate  or  branched, 
mostly  leathery;  hymenium  superfi- 
cial.— Thelephora,  C  o  r  t  i  c  i  u  m, 
Stereum. 
Order  Exobasidiales.  Reduced  and  degraded  plants 
related  to  the  preceding  families; 
basidia  undivided. 

Family  123.  Dacryomycetaceae;  124,  Tulasnellaceae; 
125,  Hypochnaceae;  126,  Exobasid- 
iaceae. 
Order  Tremellales.  Jelly  Fungi.  Reduced  and  degrad- 
ed plants  related  to  the  preceding 
families;  basidia  divided  verticall5\ 

Family  127.  Sirobasidiaceae. 

Family  128.  Tremellaceae.  Basidia  collateral,  spore 
fruits  open. — Tremella,  Exidia. 

Family  129.    Hyaloriaceae. 
Order  Auriculariales.     Ear     Fungi.     Reduced     and 
degraded  plants  related  to  the  preced- 
ing families;   basidia   divided   trans- 
versely. 

Family  130.  Auriculariaceae.  Hymenium  exposed,  on 
a  gelatinous,  foliose  or  vague  spore 
fruit. — Auricularia. 

Family  131.  Pilacraceae. 
Class  17.  TELIOSPOREAE.     Brand  Fungi.    Parasitic,  much 
reduced  plants,  producing  erumpent 
sori    (but    no    definite    spore  fruits) 


CARPOMYCETEAE  347 

consisting  of  teliospores.    (Sp.  about 
4,200.) 
Order  Uredinales.       Rusts.      Typically    with   sporidia, 
pycniospores,    aeciospores,    uredinio- 
spores  and  teliospores. 

Family  132.  Aecidiaceae.  Teliospores  free  or  fas- 
cicled.— "Puccinia,"  Dicaeoma,  Ni- 
gredo,  Uropj'xis,  Aecidium,  Phrag- 
midium,  Uromyces. 

Family  133.  Uredinaceae.  Teliospores  compacted 
into  a  crust  or  column. — "Melamp- 
sora,"  Uredo,  Cronartium. 

Family  134.  Coleosporiaceae.    Teliospores  compacted 
laterally    into    waxy    layers. — Coleo- 
sporium. 
Order  Ustilaginales.    Smuts.    Typically  with  sporidia 
and  teliospores. 

Famih"  135.  Ustilaginaceae.  Germinating  teliospore 
producing  a  septated  promycelium. — 
Ustilago,  Sphacelotheca. 

Familj'  136.  Tilletiaceae.  Germinating  teliospore  pro- 
ducing a  tubular  promycelium. — 
Tilletia,  Entyloma. 
FUNGI  IMPERFECTI.  The  "Imperfect  Fungi."  Including 
16,000  to  17,000  species  with  regard 
to  which  our  knowledge  is  quite  im- 
perfect. Most  of  them  are  regarded  as 
conidial  states  of  Ascosporeae.  The 
classification  here  given  is  merely 
provisional. 
Order  Sphaeropsidales.  Spot  Fungi.  Conidia  developed 
in  pycnidia. 

Family  137.  Sphaerioidaceae.  Pycnidia  more  or  less 
spherical,  black. — Phyllosticta,  Sphae- 
ropsis,  Septoria. 

Family  138.  Nectrioidaceae.  Pycnidia  more  or  less 
spherical,  bright  colored. — Sphaero- 
nemella,  Aschersonia. 

Family  139.  Leptostromataceae.  Pycnidia  shield- 
shaped,  black. — Leptostroma,  Lepto- 
thvrium. 


348  THE  PLANT  PHYLA 

Family  1-iO.  Excipulaceae.     Pycnidia  more    or    less 
disk-shaped,     round     or     elongated, 
black. — Excipula,  Discella. 
Order  Melanconiales.     Black-dot  Fungi.     Conidia  de- 
veloped on  a  stroma. 

Family  14 L  IMelanconiaccae.  Including  Gloeospor- 
ium,  Collctotrichum,  Melanconium, 
Pcstalozzia,  Cylindrosporium,  etc. 
Order  AIoniliales.  JMolds.  Conidia  developed  upon 
separate  conidiophores  which  do  not 
form  a  stroma. 

Family  142.  Mucedinaceae.  Conidiophores  separate, 
hyaline. — Oospora,  Monilia,  Oidium, 
Sterigmatocystis,  Botrytis,  Ramu- 
laria. 

Family  143.  Dematiaceae.  Conidiophores  separate, 
dark  or  black. — Torula,  Dematium, 
Fusicladium,  Cladosporium,  Macro- 
sporium,  Cercospora. 

Family  144.  Stilbaceae.  Conidiophores  united  into  an 
erect,  compound,  spore-bearing  body. 
— Stysanus,  Isaria,  Graphium. 

Family  145.  Tuberculariaceae.  Conidiophores  united 
into  a  compound,  cushion-like,  spore- 
bearing  body. — Tuberculina,  Fusar- 
ium,  Epicoccum. 


Phylum  Vm.  BRYOPHYTA.     The  Mossworts 

Chlorophyll-green,    small,    massive,    sexual    plants    (gameto- 

phytes),  producing  a  small,  spore-bearing  generation 

(sporophyte) 

Class  18.  HEPATICAE.  Liverworts.  Gametophytes  mostly 
bilateral,  often  thalloid,  creeping; 
sporophytes  usually  splitting  and 
containing  elaters.  (Sp.  about  4,000.) 
Order  Ricciales.  The  Riccias.  Sporophyte  globose, 
sessile,  without  columella  or  elaters. 
Family  1.  Ricciaceae.  Small  thallose  plants,  float- 
ing or  terrestrial. — Riccia. 


BRYOPHYTA  349 

Order  Axthocekotales.  Hornworts.  Sporoj)hyte  elon- 
gated, with  a  columella  and  elaters, 
two-valved. 

Family    2.  Anthocerotaccae.     Gametophyte    a    flat 
thallus. — Anthoceros. 
Order  Marchantiales.     Great  Liverworts.     Sporophyte 
rounded,  without  columella,  indehis- 
cent. 

Family    3.  Corsiniaceae. 

Family    4.  Marchantiaceae.       Gametophyte     large, 
thallose,    branching,    with   elaters. — 
Marchantia,  Conocephalus. 
Order  Jungermanniales.     Scale    Mosses.      Sporophyte 
stalked,  four-valved;  with  elaters. 

Family  5.  Metzgeriaceae.  Gametophyte  usually 
thallose,  archegones  lateral. — IMetz- 
geria,  Pellia,  Fossombronia. 

Family  G.  Jungermanniaceae.  Gametophyte  a  bi- 
lateral leafy  stem,  archegones  termi- 
nal.— Lophosia,  Bazzania,  Scapania, 
Frullania. 
Class  19.  MUSCI.  Alosses.  Gametophytes  multilateral,  usu- 
ally erect;  sporophytes  mostly  dehis- 
cent by  a  circular  lid,  and  without 
elaters.  (Sp.  about  12,600.) 
Order  Andreaeales.  Black  Mosses.  Sporophyte  short- 
stalked,  opening  by  four  to  six  longi- 
tudinal slits. 

Family    7.  Andreaeaceae.    Small  mosses. — Andreaea. 
Order  Sphagnales.     Peat   Mosses.       Sporophyte    short- 
stalked,    opening   by   a   circular   lid. 

Family  8.  Sphagnaceae.  Large  bog  mosses. — Sphag- 
num. 
Order  Bryales.  True  Mosses.  Sporophytes  mostly  long- 
staLked,  generally  opening  by  a  circu- 
lar lid,  usually  with  a  peristome. 
Sub-order  Acrocarpi.  ''Top  Mosses."  Sporophytes 
terminal  on  the  main  axis  of  the 
gametophyte. 

Family  9.  Archidiaceae;  10,  Dicranaceae  ("Turf 
Mosses") ;  11,  Leucobryaceae (" Cush- 


350 


THE  PLANT  PHYLA 


ion  Mosses");  12,  Fissidentaceae;  13, 
Calymperaceae. 

Family  14.  Pottiaceae.  Small  to  medium  plants, 
with  erect  capsules  usually  having  a 
peristome  of  10  teeth.— Weisia,  Bar- 
bula,  Phascum,  Pottia,  Encalypta. 

Family  15.  Grimmiaceae, 

Family  IG.  Orthotrichaceae.  Erect,  tufted  plants, 
with  erect  capsules  usually  with  one 
or  two  rows  of  8  or  16  teeth. — Ortlio- 
trichum,  Macomitrium. 

Family  17.  Splachnaceae.  ''Petticoat  Mosses." 
Capsule  stalked,  generally  with  an 
enlarged  base. — Splachnum. 

Family  18.  Oedipodiaceae;  19,  Disceliaceae. 

Family  20.  Funariaceae.  ''Bristle Mosses."  Capsule 
from  erect  and  regular  to  drooping 
and  curved  or  oblique;  teeth  0,  or  one 
or  two  rows  of  16  each. — Ephemerum, 
Physcomitrium,  Funaria. 

Family  21.  Schistostegiaceae;  22,  Drepanophyllaceae; 
23,  Mitteniaccae. 

Family  24.  Bryaceae.  "Wood  Mosses."  Small  to 
large  plants  with  costate  leaves,  and 
pear-shaped,  long-stalked  capsule; 
teeth  usually  in  two  whorls  of  16 
each. — Bryum. 

Family  25.  Leptostomataceae. 

Family  26.  Mniaceae.  "Wood  Mosses."  Rather 
large,  leafy  plants,  with  ovoid  to 
cylindrical,  pendent  capsule;  peri- 
stome usually  double,  each  whorl  of 
16  teeth. — Mnium. 

Family  27.  Rhizogoniaceae;  28,  Meeseaoeae;  29,  Aulo- 
comniaceae;  30,  Catascopiaceae;  31, 
Bartramiaceae. 

Family  32.  Timmiaceae.  "Bristle  Mosses."  Rather 
large  leafy  plants,  with  long-stalked 
capsules;  peristome  in  two  rows  of 
16  and  64  teeth. — Timmia. 


1 


BRYOPHYTA  351 

Family  33.  Webcraceae;  34,  Buxl^aumiaccao  ("  Hump- 
back Mosses");  35,  Georgiaccae. 

Famih' 30.  Polytrichaccae.  "Hair-caps."  I-argo, 
leafy  plants,  with  long-stalked  cap- 
sules; teeth  short  in  one  row  of  32  or 
64. — Polytrichum,  Pogonatum. 
Sub-order  Pleurocarpi.  "Side  Mosses."  Sporophytes 
terminal  on  short  lateral  axes  of  the 
gametophyte. 

Family  38.  Erpodiaceae;  39,  Hedwigiaceae;  40,  Font- 
inalaceae  ("Brook  Mosses"). 

Family  41.  Climaciaceae.  "Tree  Mosses."  Large 
erect  dendroid  plants,  with  erect  or 
recurved  capsules;  teeth  in  two  rows 
of  16  each. — Climacium. 

Family  42.  Cryphaeaceae;  43,  Leucodontaceae;  44, 
Prion odontaceae;  45,  Ptychomniaceae; 
46,  Spiridentaceae;  47,  Lepyrodonta- 
ceae;  48,  Pleurophascaceae. 

Family  49.  Neckeraceae.  More  or  less  rigid,  leafy 
plants,  with  short-stalked,  erect  cap- 
sules, having  single  or  double  peri- 
stome.— Leptodon,  Neckera. 

Family  50.  Lembophyllaceae;  51,  Entodontaceae;  52, 
Fabroniaceae;  53,  Pilotrichaceae;  54 
Nematocaceae;  55,  Hookeriaceae;  56, 
Hypopterygiaceae;  57,  Helicophyl-, 
laceae;  58,  Rhacopilaccae. 

Family  59.  Leskeaceae.  Cushion-forming,  leafy 
plants,  with  symmetrical,  erect  caj)- 
sules,  having  double  peristome. — 
Leskea,  Anomodon,  Thuidium. 

Family  60.  Leucomiaceae;  61,  Sematophyllaceae;  62, 
Rhegmatodontaceae;  63,  Brachythe- 
ciaceae;  64,  Hypnodendraceae. 

Family  65.  Hypnaceae.  "Bog  flosses."  Of  variable 
size  and  habit,  with  long-stalked 
capsules,  which  have  a  double  peri- 
stome, of  16  teeth  in  each  row. — 
Hypnum,  Amblystcgium. 


352  THE  PLANT  PHYLA 

Phylum  IX.     PTERmOPHYTA.     The  Ferns 

Chlorophyll-green,  small,  sexual  j^lants  (gametophytes),  pro- 
ducing a  large-leaved,  rooted  generation  (sporophyte). 
(Here    restricted    to    the    ferns    alone    and 
including  about  3,800  sp.) 

Class  20.  EUSPORANGIATAE.  Old-fashioned  Ferns.  Spor- 
angia developed  from  internal  cells. 
Order  Ophioglossales.  Adder-tongues.  Gametophyte 
tuberous,  subterranean;  sporophyte 
with  large  leaves,  some  parts  sporog- 
enous. 

Famil}'  1.  Ophioglossaceae.  Including  Ophioglos- 
sum,  Botrychium,  etc. 
Order  Marattiales.  Marattias.  Gametophyte  flat, 
green,  superficial;  sporophyte  with 
large  compound  leaves;  sporangia 
hypophyllous. 

Family  2.  Marattiaceae.  Large  tropical  ferns,  from 
the  Paleozoic  to  the  present. — Angi- 
opteris,  Marattia. 
Order  Isoetales.  Quillworts.  Gametophytes  dioecious 
rounded;  sporophyte  with  erect, 
crowded,  narrow  leaves;  sporangia 
epiphyllous,  basal. 

Family    3.  Isoetaceae.     Aquatic,  rush-like  plants. — 
Isoetes. 
Class  21.  LEPTOSPORANGIATAE.    Modern  Ferns.     Spor- 
angia developed  from  superficial  cells. 
Order  Filicales.    Land  Ferns.    Spores  of  one  kind;  game- 
tophytes foliose,  monoecious. 

Family  4.  Osmundaceae.  Sporangia  globose,  split- 
ting vertically. — Osmunda. 

Family  5.  Schizaeaceae;6,  Gleicheniaceae;  7,  Maton- 
iaceae;  8,  Parkeriaceae. 

Family  9.  Cyatheaceae.  Tree  Ferns.  Sporangia 
compressed,  splitting  transversely. — ■ 
Alsophila,  Cyathea,  Dicksonia. 

Family  10.  Hymenophyllaceae.  Filmy  Ferns.  Spor- 
angia compressed,  splitting  vertically. 
— Hymenophyllum,  Trichomanes. 


CALAxMOPHYTA  353 

Family  11.  Poly  pod  iaceao.  Common  Ferns.  Spor- 
angia compressed,  splitting  trans- 
versely.— Polypodium,  Asplenium, 
Nephrodium,  Adiantum,  Pteridium. 
Order  Marsiliales.  Water  Ferns.  Spores  of  two  kinds; 
gametophytes  dioecious,  rounded. 

Family  12.  Marsiliaceae.  Perennial  plants  rooted  in 
the  mud,  mostly  bearing  4-parted 
leaves. — Marsilia,  Pilularia. 

Family  13.  Salviniaceae.  Annual,  small,  floating, 
nearly  rootless  plants. — Azolla,  Sal- 
vinia. 


Phylum  X.     CALAMOPHYTA.     The  Calamites 

Minute  sexual  plants  (gametophytes),  producing  cylindrical, 
jointed    and    rooted    sporophytes    which    bear 
whorled  leaves.     (Living  species  about 
24,  but  very  many  extinct.) 

Class  22.  SPHENOPHYLLINEAE.  Wedge-leaved  Calamites. 
Paleozoic  herbaceous  plants  of  mod- 
erate dimensions   and   solid,   jointed 
stems;  long  extinct.     Isosporous. 
Order   Sphexophyllales,    including   Family   1,  Spheno- 
phyllaceae. 
Class  23.  EQUISETINEAE.  Horsetails.     Paleozoic  to  recent 
herbaceous      plants      with      hollow, 
jointed  stems.     Isosporous. 
Order  Equisetales.     Spore-bearing  cones  terminal. 

Family  2.  Equisetaceae.  With  one  living  genus. — 
Equisetum. 
Class  24.  CALAMARIXEAE.  Old  Calamites.  Paleozoic 
plants,  often  trees,  with  hollow,  in- 
creasing stems,  long  extinct.  Hetcro- 
sporous. 
Order  Calamariales,  including  Family  3,  Protocalamaria- 
ceae;  4,  Calamariaceae. 

23 


354  THE  PLANT  PHYLA 

Phylum  XL     LEPIDOPHYTA.     The  Lycopods 

Minute    gametophytes,    producing    branching,    small-leaved, 

rooted  sporophytcs.     (Living  species  about 

700,  but  very  many  extinct.) 

Class  25.  LYCOPODINEAE.    Lower  Lycopods.     Lsosporous; 
leaves  without  ligules. 
Order  Lycopodiales.     Gametophytes  much  larger  than 
the  spore. 
Family    1.  Lycopodiaceae.  Ground  Pines.    Dendroid, 

evergreen  plants. — Lycopodium. 
Familv    2.  Psilotaceae. 
Class  26.  LEPIDODENDRINEAE.     Higher    Lycopods. 
Heterosporous;  leaves  with  ligules. 
Order  Selaginellales.    Small  plants;  stems  not  thicken- 
ing. 
Family    3.  Selaginellaceae.  Club  Mosses.    Moss-like 
plants     bearing     terminal     cones. — 
Selaginella. 
Order  Lepidodendrales.      Paleozoic  and  Mesozoic  trees, 
long  extinct. 
Family    4.  Lepidodendraceae;  5,  Bothrodendraceae; 
6,  Sigillariaceae;  7,  Pleuromoiaceae. 

Phylum  XIL     CYCADOPHYTA.     The  Cycads 

IMinute  gametophytes  developed  in  naked  seeds  produced  by 

the   large,    leafy-stemmed   and   rooted   sporophj^tes; 

sperms  motile.     (Living  species  about  140,  but 

very  many  extinct.) 

Class  27.  PTERIDOSPERMEAE.     Seed   Ferns.     Paleozoic, 
fern-like  plants,  long  extinct. 
Order  Pteridospermales.     With  characters  of  the  class. 
Family    1.  Lyginopterideae;  2,  ]\ledullosae;  3,  Clad- 
oxyleae;  4,  Protopityeae;  5,  Araucari- 
oxyleae. 
Class  28.  CYCADIXEAE.    Common  Cycads.      Mesozoic  to 
present  plants  with  pinnate  leaves. 
Order  Cycadales.     With  the  characters  of  the  class. 

Family    6.  Cycadaceae.     Mostly  tropical  trees  with 
staminate  cones  onlv. — Cvcas. 


CYCADOPHYTA  355 

Family    7.  Zamiaceae.    Tropical  trees  with  staminate 
and     seed     cones. — Zamia,     Macro- 
zamia,  Dioon. 
Class  29.  BENNETTITINEAE.    Flowering-plant  Ancestors. 
Mesozoic  plants  with  pinnate  leaves, 
long  extinct. 
Order  Bennettitales.     With  the  characters  of  the  cla.ss. 
Family    8.  Bennettitaceae. 
Class  30.  CORDAITINEAE.    Conifer  Ancestors.      Paleozoic 
to   present,    trees   and    shrubs    with 
typically       parallel-veined       leaves, 
mostly  long  extinct. 
Order    Cordaitales.     Branching    trees    with    elongated 
parallel-veined  leaves.     (Extinct.) 
Family    9.  Cordaitaceae. 
Order  Ginkgoales.     Maidenhair  Trees.    Branching  trees 
with      fan-shaped,       parallel-veined 
leaves.     (All  extinct  but  one  species.) 
Family  10.  Ginkgoaceae.     But  one  genus  remaining. 
— Ginkgo. 
Order  Gxetales.     Joint  Firs.     Anomalous  woody  plants 
of  doubtful  relationship,  probably  to 
be  placed  here,  but  the  sperms  not 
motile. 
Family  11.  Ephedraceae.       Small       Equisetum-like 
shrubs  with  reduced,  opposite  leaves. 
— Ephedra. 
Family  12.   Gnetaceae.     Shrubs  and  trees  with  large, 
opposite,  pinnately  veined  leaves. — 
Gnetum. 
Family  13.    Tumboaceae.        Short,     thick-stemmed 
woody  plants  with  two  large,  oppo- 
site,    parallcl-veined    leaves. — Turn- 
boa  (Welwitschia). 

Phylum  XIII.     STROBILOPHYTA.     The  Conifers 

Minute  gametophytes  developed  in  naked  seeds  produced  by 

the  large,  leafy-stemmed  and  rooted   sporojjhyte^;   sperms 

not  motile.     (Sp.  about  400.) 

Class  31.  PINOIDEAE.     Mostly  trees  with  increasing  stents 


35a  THE  PLANT  PHYLA 

and  small  mostl}'  persistent  leaves; 
sporophylls  mostly  in  cones. 
Order  Coniferales.      jMicrosporophylls  and  megasporo- 
phylls  in  cones. 

Family  1.  Taxodiaceae.  Taxodiums.  IMicrosporo- 
phyll  with  2  to  8  sporangia;  mega- 
sporophyll  woody,  with  2  to  several 
erect  or  inverted  seeds;  *' seed-scale" 
wanting. — Taxodium,  Sequoia. 

Family  2.  Araucariaceae.  Old  Pines.  JMicrosporo- 
phyll  with  5  to  15  sporangia;  mega- 
sporophyll  woody,  with  1  inverted 
seed;  "seed-scale"  rudimentary. — 
Araucaria. 

Family  3.  Abietaceae.  Modern  Pines.  Microsporo- 
phjdl  with  2  sporangia;  megasporo- 
phyll  woody,  with  2  inverted  seeds; 
* ' seed-scale "  promin ent.  —  Pinus, 
Larix,  Picea,  Abies. 

Family  4.  Cupressaceae.  Cypresses.  Microsporo- 
phjdl  with  4  to  8  sporangia;  mega- 
sporophyll  woody,  with  1  to  many 
seeds;  no  ''seed-scale." — Cupressus, 
Chamaecyparis, 

Family  5.  Thuyopsidaceae.  Thuyas.  Microsporo- 
phyll  with  3  to  5  sporangia;  mega- 
sporophyll  woody,  with  1  to  many 
seeds. — Thuya,  Libocedrus. 

Family  6.  Juniperaceae.  Junipers.  Microsporo- 
phyll  with  4  to  8  sporangia;  mega- 
sporophyll  fleshy,  with  1  to  2  seeds. — 
Juniperus. 
Order  T.\xales.  Microsporophylls  in  cones,  megasporo- 
phylls  in  very  small  cones  or  solitary. 

Family  7.  Podocarpaceae.  Microsporophyll  with 
2  sporangia;  megasporophylls  in  very 
small  cones  or  solitary;  seed  1,  in- 
verted.— Podocarpus. 

Family  8.  Phyllocladaceae.  Microsporophjdl  with 
2  sporangia;  megasporophylls  soli_ 
tary;   seed  1,   erect. — Phyllocladus. 


AXTHOPHYTA  357 

Family  9.  Taxaceae.  Yews.  Microsporophyll  with 
3  to  5  sporangia;  megasporophyll 
solitary;  seeds  1  or  2,  erect. — Taxus, 
Torreya. 

Phylum  XIV.    ANTHOPHYTA.     The  Flowering  Plants 

Minute  gametophytes  developed  in  seeds  enclosed  in  carpels 
in  flowers,   produced  by  the  large,  leafy-stemmed  and 
rooted  sporophytes;  sperms   not   motile 
(Sp.' about  132,500.) 

Class  32.  MOXOCOTYLEDONEAE.  .Monocotyledons- 
Leaves  of  sporophj'te  alternate,  from 
the  first,  iLsually  parallel  veined; 
fibrovascular  bundles  of  stem  scat- 
tered. (Sp.  about  23,700.) 
Sub-Class  IMOXOCOTYLEDONEAE-HYPOGYXAE.  Peri- 
anth and  stamens  arising  below  the 
carpels  (carpels  superior). 
Order  Allsmatales.  Carpels  separate,  superior  to  all  other 
parts  of  the  flower. 

Family  1.  Alismataceae.  Water  Plantains.  Large- 
leaved  herbs  with  rather  large  flowers 
having  cal^'x  and  corolla  of  3  leaves 
each. — Alisma,  Sagittaria. 

Family  2.  Butomaceae;3,  Triuridaceae;4,  Scheuch- 
zeriaceae. 

Family  5.  Typhaceae.  Cat-tails.  Tall  herbs  with 
linear,  sheathing  leaves  and  cylin- 
drical-crowded flowers. — Typha. 

Family  G.  Sparganiaceae;  7,  Pandanaceae;  8,  Apon- 
ogetonaceae. 

Family  9.  Potamogetonaceae.  River-weeds.  ]\Iost- 
ly  aquatic  herbs  with  reduced  small 
flowers. — Potamogeton,  Zostera,  Zan- 
nichellia. 
Order  Liliales.  Carpels  (usually  3)  united  forming  a 
compound  pistil,  superior;  perianth 
in  two  whorls  (of  3  eacli),  corolla-like. 

Family  10.  Liliaccac.  Lilies.  Pistil,  mostly  3- 
celled;  stamens  (3. — Lilium.  Ervthron- 


358 


THE  PLANT  PHYLA 


Famib 


Family     1. 


Family 
Family 


ium,     Tulipa,      Yucca,     Asparagus, 
Allium. 

11.  Stemonaceac;  12,  Pontederiaceae;  13, 
Cyanastraceae;  14,  Philydraceae. 
Commclinaceao.  Spiderworts.  Succu- 
lent herbs  with  3  or  2-celled  pistil, 
and  6  stamens. — Commelina,  Trades- 
cant  ia. 

16.  Xyridaceae;  17,  Mayaceae. 

18.  Juncaceae.  Rushes.  Herbs  with  stiff, 
narrow  leaves,  and  1  to  3-celled  pistil. 
— Juncus. 
Eriocaulonaceae;  20,  Thurniaceae;  21, 
Rapateaceae;  22,  Naiadaceae. 
Compound  pistil  mostly  tricarpellary, 
superior;  ovules  solitary. 

23.  Cyclanthaceae. 

24.  Araceae.  Arums.  Mostly  herbs  with 
broad,  petioled  reticulate-veined 
leaves;  flowers  small,  clustered. — 
Acorus,  Symplocarpus,  Calla,  Cala- 
dium.  Arum,  Arisaema. 

25.  Lemnaceae.        Duckweeds.        Reduced 
plants  related   to  the   Araceae,  with 
flat  plant-body  floating  free  on  water. 
— Lemna,  Spirodela. 
Compound  pistil  mostly  tricarpellary, 

superior;  ovule   usually    1;   perianth 
reduced   to  rigid  scales. 
Family    2G.  Palmaceae.      Palms.      Trees  or  shrubs 
with   pinnate   or   palmate   leaves. — 
Phoenix,  Chamaerops,  Calamus,  Ore- 
odoxa,  Cocos. 
Order  Graminales.     Compound   pistil  reduced   to  2  or 
3  carpels;  ovule  solitary;  perianth  re- 
duced to  small  scales,  or  wanting. 
Restionaceae;  28,  Centrolepidiaceae;  29, 
Flagellariaceae. 
30.  Cyperaceae.     Sedges.     Grass-like  herbs 
with  3-ranked  leaves. — Cyperus,  Scir- 
pus,  Carex. 


Family    19. 
Order  Arales. 


Family 
Familv 


Familv 


Order  Palmales. 


Family    27 


Familv 


AXTIIOPHYTA  359 

Family  ol.  Poaceae.  Grasses,  with  2-ranked  leaves. 
(Sp.  about  3,o45.) 
There  aie  six  tril)es  and  several  sub-tribes,  of  which  the 
Bamboos  are  the  lowest,  while  the 
Agrostideae,  Paniceae  and  Maydeae 
are  at  the  summits  'of  as  many  di- 
verging phyletic  lines.  These  groups 
may  be  distinguished  as  follows: 

A.  Woody  })Iants;  a  joint  between  the  leaf-blade  and  the 

sheath.     1.    Bamboos.     {Bambuseae) 
Bambusa. 

B.  Herbaceous  plants;  no  joint  between   the  leaf-blade 

and  sheath. 

I.  Spikelets  with  the  larger  flowers  at  the  base. 

1.  Spikelets  typically  containing  several  to  many 

flowei's. 

a.  IMostly  arranged  in  panicles;  awns  ter- 

minal.    2.  Fescue  Grasses  (Festuceae) 
— Bromus. 

b.  Arranged  in  panicles;  awns  dorsal.     2a. 

Oat    Grasses    (Avetieae) — Avena. 

c.  Sessile    in    two   rows    on    the   opposite 

sides  of  the  main  stem.      2b.  Wheat 
Grasses  ( Triticeae) — Triticum. 

d.  Sessile  in  two  rows  on  one  side  of  a  flat- 

tened axis.        2c.  Gramma  Grasses. 
(Chlorideae) — Bouteloua. 

2.  Spikelets  containing  but  one  flower.     3.  Red- 

top  Grasses  (Agrostidcae) — Agrostis. 

II.  Spikelets  with  the  larger  flowers  at  the  top. 

1.  A  joint  above  the  empty  glumes. 

a.  Spikelets  with  five  glumes;  palets  one- 
nerved.  4.  Canary  Grasses  {Phal- 
aridcae) — Phalaris. 

2.  A  joint  below  the  empty  glumes. 

a.  Spikelets  flattened  laterally,  one-flowered. 

4a.     Rice  Grasses  (Oryzeae) — Oryza. 

b.  Spikelets  not  flattened  laterally,  one  to 

two-flowered. 
(1)  Stems    hollow,    medium    sized    to 
small.    5.    Panic  Grasses  {Paniceae)— 
Panicum. 


360 


THE  PLANT  PHYLA 


(2)  Stems  mostly  solid,  often  large  and 
tall. 

(a)  Spikelets  perfect  or  staminate, 

not  separated.  6.  Blue-stem 
Grasses  (Andropogoneae) — 
Andropogon. 

(b)  Spikelets  all  unisexual,  sepa- 
rate, monoecious.  6a.  Maize 
Grasses  (Maydeae) — Zea. 


Order  Hydrales, 
Order  Iridales. 


Sub-Class  MONOCOTYLEDONEAE-EPIGYNAE.  Peri- 
anth and  stamens  arising  above  the 
carpels;  carpels  inferior, 
with  one  family,  32,  Hydrocharitaceae. 
Compound  tricarpellary  pistil  inferior; 
whorls  of  perianth  mostly  alike  and 
regular. 

Family  33.  Amaryllidaceae.  Amaryllises.  Leaves 
narrow  to  broad,  the  veins  longi- 
tudinal.— Amaryllis,  Narcissus,  Ag- 
ave, Hypoxis. 

Family  34.  Haemodoraceae. 

Family  35.  Iridaceae.  Irises.  Leaves  sword-shaped; 
stamens  3. — Iris,  Crocus,  Sisyrinch- 
ium.  Gladiolus. 

Family  36.  Velloziaceae;  37,  Taccaceae;  38,  Dio- 
scoreaceae. 

Family  39.  Bromeliaceae.  Leaves  mostly  rosulate 
elongated  and  pointed. — Tillandsia, 
Ananas. 

Family  40.  Musaceae.  Bananas.  Large  herbs, 
often  tree-like. — Musa,  Strelitzia. 

Family    41.  Zingiberaceae. 

Family  42.  Cannaceae.  Perennial  herbs  with  pin- 
nately-veined  leaves  and  irregular 
flowers. — Canna. 

Family    43.  Marantaceae. 
Order  Orchidales.       Compound  tricarpellary  pistil  in- 
ferior;  perianth  irregular. 

Family    44.  Burmanniaceae. 

Family    45.  Orchidaceae.  Orchids.  Flowers  irregular, 


ANTHOPIIYTA 


361 


stamens  lor 2. — Cypripedium,  Orchis, 
Platanthera,  Vanilla,  Spiranthes. 
Class  33.  DICOTYLEDONEAE.     Dicotyledons.     Leaves  of 
young  sporophy  te  opposite,  sometimes 
remaininp;      so,      usually     reticulate 
veined;  fibrovascular  bundles  of  stem 
in   one  or  more  rings.     (Sp.    about 
108,800.) 
Sub-Class  DICOTYLEDONEAE-AXIFLORAE.   ''  Axis  Flow- 
ers."  Axis  of  the  flower  normally  cy- 
lindrical, spherical,  hemispherical  or 
flattened,     bearing     on     its    surface 
the    hypogynous    perianth,    stamens 
and  carpels  (or  the  stamens  may  be 
attached  to  the  corolla). 
Super-Order  .\xiflorae-Apopetalae-Polycarpellatae. 
Carpels    typically    many,    separate 
or  united;  petals  separate. 
Order  Ranales.    All  parts  of  the  flower  free  (not  united); 
carpels  separate;  typically  many. 

Family  46.  Magnoliaceae.  Magnolias.  Trees  and 
shrubs  with  many  petals  in  1  to  many 
whorls. — Magnolia,  Liriodendron. 

Family  47.  Calycanthaceae;  48,  Monimiaceae;  49, 
Cercidiphyllaceae;  50,  Trochoden- 
draceae;  51,  Leitneriaceae. 

Family  52.  Anonaceae.  Papaws.  Trees  and  shrubs 
with  6  petals  in  two  whorls.^ 
Asimina. 

Family  53.  Lactoridaceae;  54,  Gomortegaceae;  55, 
Myristicaceae;  56,  Saururaceae;  57, 
Piperaceae;  58,  Lacistemaceae;  59, 
Chloranthaceae. 

Family    ()0.  Ranunculaceae.     Buttercups.      Mostly 
herbs,   normally  with  5  i)etals  in   1 
whorl. — Myosurus,  Ranunculus,  An- 
emone, Clematis. 
Lardizabalaceae;  62,  Berberidaceae;  63, 

Menisi^ermaceae;   64,  Lauraccae. 

Nelumbaceae.     Lotuses.    Aquatic  herbs 

with  separate  carpels. — Nelumbo. 


Family 
Family 


61 


65. 


362 


THE  PLANT  PHYLA 


Family    06.  Cabombaceae;  67,  Ceratophyllaceae;  68, 
Dilleniaceae;  69,  Winteranaceae. 
Order  Ma lv ales.     Pistil  usually  of  3  to  many  carpels, 
with  as  many  cells;  stamens  normally 
indefinite,  monadelphous,  branched. 

Family    70.  Sterculiaceae. 

Family  7L  Malvaceae.  Mallows.  Herbs,  shrubs 
and  trees;  flowers  regular  with  mon- 
adelphous stamens. — Malva,  Hibis- 
cus, Althaea,  Abutilon,  Gossypium. 

Family  72.  Bombacaceae;  73,  Scytopetalaceae;  74, 
Chlaenaceae;  75,  Gonystjdaceae. 

Family  70.  Tiliaceae.  Lindens.  Mostly  trees  and 
shrubs;  flowers  regular  with  free 
stamens. — Tilia. 

Family    77.  Elaeocarpaceae;  78,   Balanopsidaceae. 

Family  79.  Ulmaceae.  Elms.  Trees  and  shrubs; 
flowers  reduced,  small,  apetalous; 
pistil  1  or  2-celled. — Ulmus,  Celtis, 
Planera. 

Family  80.  Moraceae.  Figs.  Trees,  shrubs  and 
herbs,  mostly  with  a  milky  juice; 
flowers  reduced,  smafl,  apetalous;  pis- 
til 1-celled. — Morus,  Toxylon,  Ficus, 
Humulus,  Cannabis. 

Family    81.  Urticaceae.    Nettles.  Herbs,  shrubs  and 
trees,   juice   not   milky;   flowers   re- 
duced,    small    apetalous;    pistil     1- 
celled. — Urtica,  Boehmeria. 
Order  Sarraceniales.     ''Insectivorous"  plants. 

Family  82.  Sarraceniaceae;  83,  Nepenthaceae. 
Order  Geraniales.      Pistil  of  several  carpels;  receptacle 
usually  with  an  annular  or  glandular 
disk. 

Family  84.  Geraniaceae.  Geraniums.  Herbs,  shrubs 
and  trees;  pistil  3  to  5-celled  on  an 
elongated  receptacle. — Geranium, 
Pelargonium,  Erodium. 

Family  85.  Oxalidaceae.  Sorrels.  Mostly  herbs 
with  a  sour  juice;  flowers  pentamer- 
ous. — Oxalis. 


ANTHOPHYTA 


363 


Family    80. 
Fiiiiiily    87. 

Family    88. 
Family    94. 

Family    95. 

Family  104. 


Family  105. 
Order  Guttifer 


Family  106. 
Family  107. 


Family  118 


Family  119 
Family  121 


Tropauolaceae.  Succulent,  trailing  herbs 
with  alternate,  peltate  leaves,  and 
irregular  flowers. — Tropaeolum. 

Balsaminaceae.  Touch-me-nots.  Succu- 
lent, mostly  erect  herbs  with  alter- 
nate leaves,  and  irregular  flowers. — ■ 
Impatiens. 

Limnanthaceae;  89,  Linaceae;  90,  Hum- 
iriaceae;  91,  Erythroxylaceae;  92,  Zy- 
gophyllaceae;  93,  Cneoraceae. 

Rutaceae.  Herbs,  shrubs  and  trees  usu- 
ally wuth  opposite,  glandular-dotted 
leaves,  and  regular  flowers. — Xan- 
thoxylum,  Ruta,  Ptelea,  Limonia, 
Citrus. 

Simarubaceae;  96,  Burseraceae;  97,  Meli- 
aceae;  98,  Malpighiaceae;  99,  Trigoni- 
aceae;  100,  Vochysiaceae;  101,  Poly- 
galaceae;  102,  Tremandraceae;  103, 
Dichapetalaceae. 

Euphorbiaceae.  Herbs,  shrubs  and  trees, 
mostly  with  a  milky  juice;  flowers 
diclinous;  pistil  usually  3-celled. — 
Euphorbia,  Croton,  Ricinus,  jManihot. 

Callitrichaceae. 
.\LES.     Pistil  mostly  of  2  or  more  carpels; 
stamens  usually  indefinite;  endosperm 
usually  wanting. 

Theaceae.  Shrubs  and  trees  with  regular 
flowers. — Thea,    Gordonia,    Stuartia. 

Cistaceae;  108,  Guttiferaceae;  109,  Eu- 
cryphiaceae;  110,  Ochnaceae;  111, 
Dipterocarpaceae;  112,  Caryocaraceae 
113,  Quiinaccae;  114,  ]\larcgraviaceae; 
115,  Flacourtiaceae;  116,  lii.xaceae; 
117,  Cochlospermaceae. 

Violaceae.  Violets.  Herbs  and  shrubs 
and  trees,  with  irregular  flowers  and 
tficarpellary  pistil. — \''iola. 

Malesherbiaceao;  120,  Turneraceae. 

Passifloraceae.    Pa.ssion  Flowers.    Climb- 


364  THE  PLANT  PHYLA 

ing   herbs   and   shrubs   with  regular 
flowers. — Passiflora. 

Family  122.  Achariaceae;  123,  Caricaceae;  124, 
Stachyuraceae;  125,  Koeberliniaceae. 
Order  Rhoedales.     Pistil  of  two  or  more  united  carpels, 
mostly  one-celled  with  parietal  pla- 
centae. 

Family  126.  Papaveraceae.  Poppies.  Perianth  2  to 
4-merous,  stamens  indefinite,  pistils 
2  to  many  carpellary. — Eschscholtzia, 
Sanguinaria,  Argemone,  Papaver, 
Bicuculla. 

Family  127.  Tovariaceae. 

Family  128.  Nymphaeaceae.  Water  lilies.  Aquatic 
herbs  with  floating  leaves. — Nym- 
phaea,  Castalia,  Victoria. 

Family  129.  Moringaceae;  130,  Resedaceae;  131,  Cap- 
paridaceae. 

Family  132.  Brassicaceae.  Mustards.  Perianth  4- 
merous,  stamens  6  or  4,  pistil  2-car- 
pellary. — Sinapis,  Brassica,  Rapha- 
nus,  Bursa,  Alyssum. 
Order  Caryophyllales.  Pistil  usually  of  3  or  more  united 
carpels,  mostly  1-celled;  stamens  as 
many  or  twice  as  many  as  the  petals. 

Family  133.  Caryophyllaceae.  Pinks.  Mostly  herbs, 
with  opposite  leaves;  ovules  many  on 
a  central  placenta. — Silene,  Lychnis, 
Dianthus,  Alsine,  Paronychia. 

Family  134.  Elatinaceae. 

Family  135.  Portulacaceae.  Mostly  succulent  herbs 
with  2  sepals  and  4  to  5  petals. — 
Portulaca,  Claytonia. 

Family  136.  Aizoaceae;  137,  Frankeniaceae;  138, 
Fouquieraceae;  139,  Tamaricaceae. 

Family  140.  Salicaceae.  WiHows.  Shrubs  and  trees 
with  alternate  leaves  and  no  perianth. 
— Salix,  Populus. 

Family  141.  Podostemonaceae;  142,  Hydrostachyda- 
ceae;  143,  Phytolaccaceae;  144,  Basel- 
laceae. 


ANTllOPllYTA  365 

Family  145.  Amaranthaceae.     Mostly      herbs     and 

shrubs    with    opposite    or    alternate 

leaves;  perianth  harsh. — Amaranthus, 

Celosia,  Froelichia. 
Family    146.  Chenopodiaccae.      Mostly  herbs    and 

shrubs    with    alternate    or    opposite 

leaves;  perianth  soft. — Beta,  Cheno- 

podium,  Atriplex,  Salsola. 
Family  147.  Polygonaceae.     Herbs,  shrubs  and  trees, 

with  alternate,  rarely  opposite  leaves; 

perianth       petal  -  like.  —  Eriogonum, 

Rheum,     Polygonum,      Fagopyrum, 

Coccoloba. 
Family  148.  Nyctaginaceae;    149,    Cynocrambaceae; 

150,  Batidaceae. 
Super-Order  Axiflorae-Gamopetalae-Polycarpel- 

LATAE.       Carpels     typically     many, 

united;  petals  united. 
Order  Prlmulales.     Pistil  mostly  1-celled,  with  a  central 

placenta;    stamens    mostl}^    opposite 

the  corolla  lobes. 
Family  151.  Primulaceae.      Primroses.      Herbs  with 

showy  flowers. — Primula,  Cyclamen, 

Dodecatheon. 
Family  152.  Plantaginaceae.    Plantains.    Herbs  with 

reduced    flowers;    stamens    alternate 

with  the  petals. — Plantago. 
Family  153.  Plumbaginaceae;  154,  Theophrastaceae; 

155,  Myrsinaceae. 
Order  Ericales.      Pistil  more  than  1-celled,  with  many 

minute  seeds;  stamens  alternate  with 

the  corolla  lobes. 
Family  156.  Clethraceae. 
Family  157.  Ericaceae.     Heaths.     Shrubs  and  small 

trees  with  mostly  evergreen  leaves; 

anthers  opening  bj^  a  terminal  pore. — 

Rhododendron,  Kalmia,  Arctostaph}-- 

los,  Vaccinium,  Erica. 
Family  158.  Epacridaceae;  159,  Diapensiaccac;  160, 

Pirolaceae;  161,  Lennoaceao. 
Order     Ebenales,      with     four     families      of     mostly 


THE  PLANT  PHYLA 

tropical  trees. — 162,  Sapotaceae;  163, 
Ebenaceae;  164,  Symplocaceae;  165, 
StjTacaceae. 
Super-Order  Axiflorae-Gamopetalae-Dicarpellatae. 
Carpels  typicall}^  two,  united;  petah 
united. 
Order  Polemoniales.  Corolla  regular;  stamens  as  many 
as  the  corolla  lobes;  leaves  mostly 
alternate. 

Family  166.  Polemoniaceae.  Phloxes.  Mostly  herbs 
with  alternate  or  opposite  leaves; 
pistil  tricarpellary. — Phlox  Gilia,  Pol- 
emonium. 

Family  167.  Convolvulaceae.  IMorning  Glories.  Most- 
ly herbs  and  shrubs  with  alternate 
leaves;  pistil  mostly  bicarpellary. 
— Convolvulus,  Ipomoea,  Evolvulus, 
Cuscuta. 

Family  168.  Hydrophyllaceae.  Soft  herbs;  pistil  bi- 
carpellary.— Hydrophyllum,  P  h  a  - 
celia. 

Family  169.  Borraginaceae.  Forget-me-nots.  Herbs, 
shrubs  and  trees;  pistil  bicarpellary, 
4-celled. — Heliotropium,  B  o  r  r  a  g  o , 
Myosotis,  Mertensia,  Lithospermum. 

Family  170.  Nolanaceae. 

Family  171.  Solanaceae.  Nightshades.  Mostly  herbs 
and  shrubs;  pistil  bicarpellarj',  mostly 
2-celled. — Solanum,  Atropa,  Physalis, 
Capsicum,  Datura,  Nicotiana,  Pe- 
tunia. 
Order  Gentianales.  Corolla  regular;  stamens  as  many  as 
the  corolla  lobes;  leaves  opposite. 

Family  172.  Oleaceae.  Olives.  Mostly  shrubs  and 
trees;  stamens  2  or  4;  ovary  2-celled. 
— Olea,  Syringa,  Jasminum,  Fraxinus. 

Family  173.  Salvadoraceae;  174,  Loganiaceae. 

Family  175.  Gentianaceae.  Mostly  herbs  with  limpid 
juice;  ovary  usually  1-celled. — Gen- 
tiana,  Eustoma,  Menyanthes. 

Family  176.  Apocynaceae.     Trees,  shrubs  and  herbs 


ANTHOPIIYTA  3(37 

witli  milky  juice;  ovarj'  2-celled,  or  of 
two  separated  carpels. — Apocynum, 
Vinca,  Nerium. 

Family  177.  Asclepiadaceae.  Alilkweeds.  Herbs  and 
shrubs  with  milky  juice;  ovary  of 
two  separated  carpels. — Asclepias, 
Ceropegia,  Stapelia,  Hoya. 
Order  Scrophulariales.  Corolla  mostly  irregular;  sta- 
mens fewer  than  the  corolla  lobes; 
ovules  many. 

Family  178.  Scrophulariaceae.  Snapdragons.  Mostly 
herbs;  ovary  2-celled;  seeds  endo- 
spermous. — Verbascum,  Antirrhinum, 
Scrophularia,  ]\Iimulus,  Veronica, 
Gerardia,  Castilleia,  Pedicularis. 

Family  179.  Bignoniaceae.  Catalpas.  Mostly  trees 
and  shrubs;  ovary  1  or  2-celled;  seeds 
without  endosperm. — Bignonia,  Cat- 
alpa,  Tecoma. 

Family  180.  Pedaliaceae;  181,  Martyniaceae;  182, 
Orobanchaceae;  183,  Gesneraceae; 
184,  Columelliaceae;  185,  Lentibu- 
lariaceae;  186,  Globulariaceae;  187, 
Acanthaceae. 
Order  Lamiales.  Corolla  mostly  irregular ;  stamene  fewer 
than  the  corolla  lobes;  ovules  usually 
solitary. 

Family  188.  Myoporaceae;  189,  Phrymaceae. 

Family  190.  Verbenaceae.  Herbs,  shrubs  and  trees, 
with  usually  undivided  stigma. — 
Verbena,  Lantana,  Lippia,  Tectona, 
Vitcx. 

Family  191.  Lamiaceae.  Mints.  Mostly  herbs  and 
shrubs,  aromatic,  with  usually  bifid 
stigma. — Lavandula,  Nepeta,  ^Salvia, 
Thvmus,  Mentha,  Coleus. 
Sub-Class  DICOTYLEDOXEAE-CALYCTFLORAE.  "Cup 
Flowers."  Axis  of  the  flower  nor- 
mally expanded  into  a  disk  or  cup, 
bearing  on  its  margin  the  perianth  and 


368  THE  PLANT  PHYLA 

stamens    (or    the  latter  may  be  at- 
tached to  the  corolla). 
Super-Order  Calyciflorae-Apopetalae.  Petals  separate. 
Carpels    many   to   few,    separate   to 
united,  superior  to  inferior. 
Order  Rosales.     Flowers  usually  perfect,  regular  or  irregu- 
lar; carpels  from  wholly  separate  to 
more  or  less  united,  sometimes  over- 
grown by  the  axis-cup;  styles  distinct. 
-   Family  192.  Rosaceae.     Roses.    Herbs,   shrubs    and 
trees,    with   mostly  alternate  leave3 
and  indefinite  stamens;  carpels  from 
many  to  one,  free. — Potentilla,  Fra- 
garia,  Spiraea,  Rosa. 

Family  193.  IVIalaceae.  Apples.  Shrubs  and  trees, 
with  alternate  leaves,  and  usually 
many  stamens;  carpels  few,  more  or 
less  united  to  the  axis  cup. — Malus, 
Pirus,  Crataegus. 

Family  194.  Prunaceae.  Plums.  Shrubs  and  trees 
with  alternate  leaves,  and  many 
stamens;  carpel  one,  in  the  bottom 
of  the  deep  cup,  becoming  a  drupe  on 
ripening. — Prunus,  Amygdalus. 

Family  195.  Crossosomataceae;  196,  Connaraceae. 

Family  197.  Mimosaceae.  The  Mimosas.  Trees, 
shrubs  and  herbs,  with  alternate, 
mostly  compound  leaves;  flowers 
regular;  stamens  10  or  more,  usually 
separate;  carpel  one,  ripening  into  a 
legume. — Acacia,  Mimosa. 

Family  198.  Cassiaceae.  The  Sennas.  Trees,  shrubs 
and  herbs,  with  alternate,  mostly 
compound  leaves;  flowers  irregular; 
stamens  10  or  less,  usually  separate; 
carpel  one,  ripening  into  a  legume. — 
Cassia,  Caesalpinia,  Gleditsia,  Gym- 
nocladus. 

Family  199.  Fabaceae.  The  Beans.  Herbs,  and  some 
shrubs  and  trees,  with  alternate, 
mostly  compound  leaves;  flowers  ir- 


ANTHOPHYTA 


369 


regular;  stamens  10  or  less,  usually 
united;  carpel  one,  ripening  into  a 
legume. — Lupinus,  Medicago,  Trifo- 
lium,  Robinia,  Vicia,  Pisum,  Phaseo- 
lus. 

Family  200.  Saxifragaceae.  Saxifrages.  Herbs  with 
alternate  or  opposite  leaves;  flowers 
regular;  stamens  8  to  10;  carpels  2, 
superior. — Saxifraga,  Heuchera,  ]\lit- 
ella. 

Family  201.  Hydrangeaceae.  Hydrangeas.  Shrubs 
and  trees  with  mostly  opposite  leaves; 
flowers  regular;  stamens  8  to  40; 
carpels  2  to  5,  united,  more  or  less 
overgrown  by  the  axis-cup. — Phila- 
delphus,  Hydrangea. 

Family  202.  Grossulariaceae.  Gooseberries.  Shrubs 
with  alternate  leaves;  flowers  regu- 
lar; stamens  5;  carpels  2  to  several, 
wholly  overgrown  by  the  fleshy  axis- 
cup. — Ribes. 

Family  203.  Crassulaceae;  204,  Droseraceae;  205, 
Cephalotaceae;  206,  Pittosporaceae; 
207,  Brunelliaceae;  208,  Cunoniaceae; 
209,  Myrothamnaceae;  210,  Bruni- 
aceae;  211,  Hamamelidaceae;  212, 
Casuarinaceae;  213,  Eucommiaceae. 

Familj'  214.  Platanaceae.  Trees  with  alternate 
leaves  and  reduced,  monoecious  flow- 
ers in  globular  heads;  no  perianth. — 
Platanus. 
Order  Myrtales.  Flowers  usually  perfect,  regular; 
pistils  several,  united,  usually  in- 
ferior. 

Family  215.  Lythraceae.  Herbs,  shrubs  and  trees, 
usuall}"  with  o])posite  leaves;  pistil 
free. — Lythrum,  Cuj)hea. 

Family  216.  Sonneratiaceae;  217,  Punioaceae;  218, 
Lecythidaceac;  219,  Mela.^tomataceae. 

Family  220.  Myrtaceac.  Myrtles.  Trees  and  shrubs 
with    opposite    or    alternate    leaves; 

24 


370  THE  PLANT  PHYLA 

stamens  indefinite;  pistil  2  to  many- 
celled,  inferior. — Myrtus,  Pimenta, 
Eugenia,  Jambosa,  Eucalyptus,  Mal- 
aleuca. 

Family  221.  Combretaceae;  222,  Rhizophoraceae. 

Famil}'  223.  Oenotheraceae.  Evening  Primroses. 
Mostly  herbs,  with  opposite  or  alter- 
nate leaves;  stamens  1  to  8;  pistil  usu- 
ally 4-celled,  inferior. — Epilobium, 
Anogra,  Oenothera,  Gaura,  Fuchsia, 
Circaea. 

Family  224.  Halorrhagidaceae;  225,  Hippuridaceae; 
226,  Cynomoriaceae;  227,  Aristoloch- 
iaceae;  228,  Rafflesiaceae;  229,  Hyd- 
noraceae. 
Order  Cactales.  Flowers  regular  and  perfect;  pistil 
syncarpous,  1-celled,  with  parietal 
placentae,  inferior;  mostly  leafless 
plants. 

Family  230.  Cactaceae.  Cactuses.  Fleshy-stemmed, 
mostly  leafless  plants. — Peireskia, 
Opuntia,  Cereus,  Carnegiea,  Echino- 
cactus.  Cactus,  Melocactus,  Rhipsalis. 
Order  Loasales.  Flowers  regular  and  perfect  or  diclinous; 
pistil  syncarpous,  1-celled,  with  pa- 
rietal placentae,  inferior;  leaves  ample. 

Family  231.  Loasaceae.  Star  Flowers.  Erect  herbs 
with  perfect,  regular  flowers,  and 
many  stamens. — MentzeHa,   Loasa. 

Family  232.  Cucurbitaceae.  Melons.  Mostly  climb- 
ing herbs  with  but  3  stamens. — 
Cucurbita,  Cucumis,  Lagenaria,  Cit- 
rullus,  Momordica. 

Family  233.  Begoniaceae.  Begonias.  Mostly  erect 
herbs,  with  diclinous  flowers  and 
many  stamens. — Begonia. 

Family  234.  Datisaaceae;  235,  Ancistrocladaceae. 

Order  Celastrales.      Flowers  regular,  rcceptacular  disk 

annular  or  turgid,  sometimes  adnate 

to  the  1  to  several-celled  pistil,  the 

latter  sometimes  inferior;  ovules  few. 


ANTHOPIIYTA  371 

Family  236.  Rhainnaccac.  Bucktliorns.  Erect  trees 
and  shrubs. — Rhainnus,  Ceanothus, 
Colletia. 

Family  237.  Vitaceae.  Grapes  Woody  climbers. — 
Vitis,     Parthenocissus,     Ampelopsis. 

Family  238.  Celastraceae;  239,  Buxaceae;  240,  Aquil- 
foliaceae;  291,  Cyrillaceae;  242,  Penta- 
phyllaceae;  243,  Corynocarpaceae;  244, 
Hippocrateaceae;  245,  Stackhousi- 
aceae;  246,  Staphyleaceae;  247,  Geis- 
solomataceae;  248,  Penaeaceae;  249, 
Oliniaceae;  250,  Thymelaeaceae;  251, 
Hernandiaceae;  252,  Elacagnaceae; 
253,  Myzodendraceac;  254,  Santala- 
ceae;  255,  Opiliaceae;  256,  Grub- 
biaceae;  257,  Olacaceae. 

Family  258.  Loranthaceae.  Mistletoes.  Parasitic 
herbs  or  shrubs  with  opposite  or 
alternate  leaves;  flowers  perfect  or 
diclinous,  apetalous;  pistil  1-celled, 
inferior. — Loranthus,  Viscum,  Phor- 
adendron,  Razoumofskya. 

Family  259.  Balanophoraceae. 
Order  Sapindales.      Flowers  mostly  regular,  disk  tumid 
(or  wanting) ;  pistil  1  to  several-celled, 
sometimes  inferior;  ovules  1  to  2. 

Family  260.  Sapindaceae.  Mostly  tropical  trees  and 
shrubs,  with  alternate  leaver,  and 
regular  flowers. — Sapindus,  Koelreu- 
teria. 

Family  261.  Hippocastanaceae.  Buckej'es.  Trees 
and  shrubs  with  opposite,  palmate 
leaves,  and  large,  irregular  flowers; 
pistil  superior. — Aesculus. 

Family  262.  Aceraceae.  Maples.  Trees  and  shrubs 
with  opposite,  palmate  or  pinnate 
leaves,  and  small,  regular  flowers; 
pistil  superior. — Acer. 

Family  263.  Sabiaceae;  264,  Icacinaceae;  265,  Meli- 
anthaceae;  266,  Empetraccue;  267, 
Coriariaceae. 


372  THE  PLANT  PHYLA 

Family  268.  Anacardiaceae.  Sumachs.  Trees  and 
shrubs  with  alternate  pinnate  leav^es; 
and  small  flowers  with  superior  or 
inferior,  1  to  5-celled  pistil. — Rhus, 
JMangifera,  Cotinus. 

Family  269.  Juglandaceae.  Walnuts.  Trees  and 
shrubs,  with  alternate,  pinnate  leaves; 
and  small  much  reduced  flowers 
with  inferior,  1-celled  pistil. — Juglans, 
Hicoria. 

Family  270.  Betulaceae.  Birches.  Trees  and  shrubs 
with  alternate,  pinnate  leaves,  and 
diclinous  flowers  in  aments;  pistil  1 
to  2-celled,  superior  or  inferior. — 
Betula,  Alnus,  Corylus,  Ostrya,  Car- 
pinus. 

Family  271.  Fagaceae.  Beeches.  Trees  and  shrubs 
with  alternate,  pinnate  leaves  and 
diclinous  flowers  in  aments;  pistils  2 
to6-celled,  inferior. — Fagus,  Castanea, 
Quercus. 

Family  272.  Myricaceae;  273,  Julianaceae;  274,  Pro- 
teaceae. 
Order  Umbellales.  Flowers  regular,  usuall}^  perfect, 
disk  adherent  to  the  mostly  bicar- 
pellary  pistil  which  is  inferior  and  2- 
celled;  ovules  1  in  each  cell. 

Family  275.  Araliaceae.  Ginsengs.  Mostly  trees 
and  shrubs;  pistil  2  to  15-carpellary; 
fruit  a  berry. — Aralia,  Hedera,  Panax. 

Family  276.  Apiaceae.  Parsleys.  Mostly  herbs; 
pistil  bicarpellary;  fruit  dry,  splitting 
vertically;  inflorescence  umbellate. — 
Sanicula,  Coriandrum,  Apium,  Cicuta, 
Pastinaca,  Foeniculum,  Ferula,  Hera- 
cleum,  Daucus. 

Family  277.  Cornaceae.  Cornels.  Mostly  shrubs  and 
trees  with  usually  opposite  leaves; 
pistil  2  to  4-carpellary;  fruit  a  drupe. 
— Cornus,  Nyssa. 


ANTHOPHYTA  373 

Super-Order  Calyciflorae-Gamopetalae.  Petals  united. 
Carpels  few,  united,  inferior. 

Order  Rubiales.     Flowers  regular  or  irregular;  ovary  2 
to  8-celled;  ovules  2  to  many. 
Family  278.  Rubiaceae.     Coffees.    Trees,  shrubs  and 
herbs  with  opposite  or  whorled  leaves 
and  mostly  regular  flowers. — Galium, 
Houstonia,  Cinchona,  Coffea,  IMitch- 
ella. 
Family  279.  Caprifoliaceae.     Honeysuckles.    Mostly 
woody  plants,   with  opposite  leaves 
and  mostly  irregular  flowers. — Sam- 
bucus.  Viburnum,  Linnaea,  Lonicera. 
Family  280.  Adoxaceae;  281,  Valerianaceae;  282,  Dip- 
sacaceae. 

Order  Campaxulales.  Flowers  regular  to  irregular, 
stamens  mostly  free  from  the  corolla; 
ovary  1  to  several-celled;  ovules  1 
to  8. 
Family  283.  Campanulaceae.  Bellworts.  Mostly 
herbs;  stamens,  usually  5,  free  from 
the  style. — Campanula,  Lobelia. 
Famil}'  284.  Goodeniaceae;  285,  Stylidiaceae;  286, 
Calyceraceae. 

Order  Asterales.  Composites.  Flowers  regular  to  irregu- 
lar, collected  into  involucrate  heads; 
calyx  small  and  often  forming  a 
"pappus"  or  wanting;  stamens  5, 
epipetalous,  mostly  with  their  an- 
thers connate;  carpels  2,  united, 
inferior,  with  one  style  which  is 
2-branched  above;  ovule  one,  erect, 
anatropous.  An  immense  order 
(commonly  regarded  as  a  family) 
of  more  than  14,300  species,  which  are 
usually  distributed  among  fourteen 
tribes,  all  of  which  are  here  raised 
to  families.  In  the  following  arrange- 
ment the  Helianthaceae  are  regarded 
as  the  lowest,  from  which  the  two 
princij)al   phyletic  lines  have  arisen. 


374  THE  PLANT  PHYLA 

culminating  on  the  one  hand  in  the 
Eupatoriaceae,  and  on  the  other  in  the 
Lactucaceae. 

Key  to  the  Families  of  Asterales 

A.  Pappus  not  capillary;  plants  typically  large 

and  coarse. 
L  Receptacle  chaffy. 

1.  Usually  with  ray  flowers — 287.    Heli- 
anthaceae. 

2.  Without  ray  flowers — 288.    Ambros- 
iaceae. 

IL  Receptacle  naked  (rarely  chaffy). 

1.  Anthers  tailless. 

a.  Involucral    bracts    mostly  in    2 

series — 289.     Heleniaceae. 

b.  Involucral     bracts     in      many 

series — 290.      Ardotidaceae. 

2.  Anthers    tailed  or  mucronate — 291. 
Calendulaceae. 

B.  Pappus  bracteose,  none,  or  capillary;  recep- 

tacle usually  naked;  plants  typically 
low  to  medium  sized. 
L     Usually   without   ray  flowers;   anthers 
tailed — 292.     Inulaceae. 

C.  Pappus  from  short  bracteose  to  capillary  or 

none;  receptacle  naked;  plants  typi- 
cally medium  sized. 

L  Usually  with  ray  flowers — 293.  Aster- 
aceae. 

IL  Without  ray  flowers;  style  branches 
filiform,  hispidulous. — 294.  Vernoni- 
aceae. 

III.  Without  ray  flowers;  style  branches 
clavate,  papillose — 295.  Eupatoriaceae. 

D.  Pappus   a   short   crown  or  none;  involucral 

bracts     dry,     scarious,     imbricated; 
plants  typically  medium  sized. 
I.  Usually    with   white  ray  flowers — 296. 
Anthettiidaceae. 


ANTHOPHYTA  375 

E.  Pappus   capillary;    involucral  bracts   mostly 

valvate,  not  scarious;  plants  larger. 
I.    With  or  without  rays— 297.  Senecionid- 
accae. 

F.  Pappus     mostly     capillary,     plants     usually 

rather  large  and  stout. 

I.  Tnvolucral  bracts  much  imbricated. 

1.  Flowers  all  tubular,  receptacle  usu- 
'  ally  bristly— 298.     Carduaceae. 

II.  Invoiucral  bracts  little  imbricated. 

1.  Flowers  all  labiate,  receptacle  usu- 
ally naked— 299.     Mutisiaceae. 

2.  Flowers  all  ligulate,  receptacle  usu- 
ally naked— 300.     Lactucaceae. 

Family  287.  Helianthaceae.       Sunflowers.       Herbs; 
calyx  not  capillary;  receptacle  chaffy; 
usually  rayed;  mostly  large,   coarse 
plants.— Helianthus,     Zinnia,     Rud- 
beckia,  Silphium. 
Family  288.  Ambrosiaceae.        Ragweeds.        Herbs; 
calyx  not  capillary;  receptacle  chaffy; 
rayless;  mostly  large,  coarse  plants. 
—Ambrosia,  Xanthium. 
Family  289.  Heleniaceae.    False  Sunflowers.    Herbs; 
calyx  not  capiUary;  receptacle  naked; 
rayed    or    rayless;    anthers    tailless; 
medium     sized     plants.— Helenium, 
Gaillardia. 
Family  290.  Arctotidaceae.    Gazanias.    Herbs;  calyx 
not     capillary;     receptacle     naked; 
anthers  tailless.  South  African  plants. 
— Gazania,  Arctotis. 
Family  291.  Calendulaceae.        Marigolds.        Herbs; 
calyx  not  capillary;  receptacle  naked; 
anthers  tailed.       Old  AVorld  jilants, 
mostly   tropical— Calendula. 
Family  292.  Inulaceae,     Everlastings.     Herbs,  with 
some  shrubs  and  small  trees;  calyx 
from  bracteose  to  capillary;  receptacle 
usually   naked;   anthers   tailed;   usu- 
ally   rayless;    mostly    low    plants.— 


376  THE  PLANT  PHYLA 

Antennaria,  Gnaphalium,  Helichry- 
sum,  Inula. 

Family  293.  Astcraceae.  Asters.  Herbs  and  under- 
shrubs;  calyx  from  bracteose  to  capil- 
lary; receptacle  naked;  usually  rayed; 
medium  sized  plants. — Aster,  Solid- 
ago,  Erigeron,  Bellis,  Baccharis. 

Family  294.  Vernoniaceae.  Ironweeds.  Herbs; 
calyx  from  bracteose  to  capillary; 
receptacle  naked;  rayless;  style- 
branches  fiUform,  hispidulous;  me- 
dium sized  plants. — Vernonia,  Ele- 
phantopus. 

Family  295.  Eupatoriaceae.  Blazing  Stars.  Herbs; 
calyx  from  bracteose  to  capillary; 
receptacle  naked;  rayless;  style- 
branches  thickened  upward,  papillose; 
medium  sized  plants. — Lacinaria, 
Eupatorium,  Kuhnia. 

Family  296.  Anthemidaceae.  Camomiles.  Herbs, 
shrubs,  and  small  trees;  calyx  a  short 
crown  or  wanting;  receptacle  chaffy  or 
naked;  usually  with  white  rays; 
mostly  medium  sized  plants. — An- 
themis,  Chrysanthemum,  Artemisia. 

Family  297.  Senecionidaceae.  Groundsels.  Herbs, 
shrubs,  and  trees;  calyx  capillary; 
receptacle  naked;  rayed  or  rayless; 
mostly  medium  sized  plants. — Sene- 
cio,  Arnica. 

Family  298.  Carduaceae.  Thistles.  Herbs;  calyx 
mostly  capillary;  receptacle  usually 
bristly  (not  chaffy);  rayless;  mostly 
stout  plants. — Carduus,  Arctium, 
Cnicus. 

Family  299.  Mutisiaceae.  Mutisias.  Herbs,  shrubs, 
and  small  trees;  calyx  mostly  capil- 
lary; receptacle  usually  naked;  flow- 
ers all  two-lipped,  so  no  proper  rays; 
mostly  medium  sized  tropical  plants. 
— Mutisia,  Chaptaha. 


ANTHOPHYTA  377 

Family  300.  Lactucaccae.  Lettuces.  Herbs  with  a 
milky  juice;  calyx  mostly  capillar}'-; 
receptacle  usually  naked;  flowers  all 
ligulate,  so  no  proper  rays;  medium 
sized  to  small  plants. — Lactuca,  Hier- 
acium,  Cichorium,  Taraxacum,  (Leon- 
todon). 

REFERENCE  BOOKS 

A.  Engler  and  K.  Prantl,  Die  NaturUchen  Pflamenfamilien, 
Leipzig,  1889  to  1909. 

C.  E.  Bessey,  A  Synopsis  of  Plant  Phyla,  Lincoln,  1907. 

A.  Engler  and  E.  Gilg,  Syllabus  der  Pflanzenfamilicn,  Berlin, 
1912. 

C.  E.  Bessey,  Revisions  of  Sortie  Plant  Phyla,  Lincoln,  1914. 


Chart  to  Show  Relationship  of  the  Plant  Phyla. 


Chart  TO  Show  Relationship  of  the  Ohdehs  of  Anthophyta. 

APPROXIMATE  NUMBERS  OF   SPECIES  IN    THE  ORDERS 
OF  ANTHOPHYTA. 

Alismatales.  409;  Liliales,  3370;  Arales,  1052;  Palmalcs.  1085; 
Graminales,  5795;  Hydrales,  53;  Iridales,  4419;  Orchidales,  7578; 
Ranales,  5551;  Malvales,  3829;  Sarraconiales,  GO;  Gcranialos,  92G8; 
Guttifcralcs,  3138;  Rhoedales,  2856;  C'aryophyllalos,  4330;  Priinulalcs, 
1581;  Ericales.  1730;  Ebonalcs,  1136;  Polcmoniales,  4112;  Gentian- 
ales,  4664;  Scrophulariales,  7081;  Lamiales.  4119;  Resales,  14261; 
Myrtales,  7323;  Cactales,  1168;  Loasales,  1392;  Cclastrales,  2741; 
Sapindalcs,  2903;  Umbellales,  2809;  Rubialcs,  5063;  Campanulales, 
1539;  Astcralcs,  14324. 


INDEX 


Abies,  281,  356 
Abiotaccae,  279,  356 
Abrotanin,  149 
Abutilon,  362 
Acacia,  368 
Acanthaceac,  367 
Acarospora,  340 
Acarosporaceae,  340 
Acer,  371 
Aceraccae,  371 
Acervuli,  239 
Acetabularia,  192,  336 
Acetic  acid,  140 
Achariaceae,  364 
Achene,  312 
Achlya,  335 
Acids,  18,  139 
Aconitin,  149 
Acorn,  311,  325 
Acorns,  300,  358 
Acrocarpi,  252,  349 
Acrospermaccae,  343 
Acrotylaceae,  339 
Actinocyclus,  334 
Actinodiscaceae,  334 
Actinodiscus,  181,  334 
Actinoniorphic.  292,  322 
Adder-tongues,  257,  352 
Adiantuni,  259,  353 
Adoxaceae,  373 
Aecidiaceae,  347 
Aecidiospores,  233 
Accidium,  234,  347 
Aeciospores,  233 
Aerobic  respiration,  91 
Aesculin,  149 
Aesculus,  371 
Agaricaccac,  229 
Agaricales,  229,  345 
Agarics,  345 
Agaricus,  229,  345 


Agathis,  279 
Agave,  320,  360 
Agrostideae,  359 
Agrostis,  359 
Aizoaceae,  364 
Alaria,  337 

Albuginaceae,  187,  335 
Albugo,  188 
Albumens,  151 
Albuminoids,  152 
Albumoses,  152 
Alcohols,  141 
Aleuron,  14 
Alisma,  289,  357 
Alismataceae,  357 
Alismatales,  295,  357 
Alkaloids,  18,  149 
Allium,  300,  358 
Almond,  314 
Alnus,  372 
Alsine,  364 
Alsophila,  352 
Alternate  leaves,  292 
Alternation  of  Generations,  242 
Althaea,  305,  362 
Alyssum,  364 
Amanita,  345 
Amaranthaceae,  365 
Amaranthus,  365 
Amaryllidaceae,  360 
Amaryllis,  298,  360 
Amaryllises,  360 
Amblystegium,  351 
Ambrosia,  375 
Ambrosiaceae,  375 
Ampelopsis,  371 
Amphipleura,  334 
Amphisi)haeriaceae,  343 
Amygdalin,  148 
Amygdalus,  368 
Amylase,  153 


381 


382 


INDEX 


Aniyluni,  147 
Anabacna,  165 
Anacardiaceae,  372 
Anaerobic  respiration,  91 
Ananas,  360 
Anauliaceae,  334 
Ancistrocladaceae,  370 
Ancylistaceae,  335 
Andreaea,  251,  349 
Andreaeaceae,  349 
Andreaeales,  251,  349 
Andropogon,  360 
Andropogoneae,  360 
Anemone,  291,  361 
Anemophilous,  321 
Angiopteris,  352 
Angiospermous,  330 
Animal  Kingdom,  171 
Animals,  172,  332 
Anogra,  370 
Anomodon,  351 
Anonaceae,  361 
Antennaria,  376 
Anthemidaceae,  376 
Anthemis,  376 
Anther,  292 
Antheridial  cells,  174 

disks,  246 

gametophytes,  258 
Antherids,  186 
Anthoceros,  245,  349 
Anthocerotaceae,  349 
Anthocerotales,  349 
Anthocyanin,  156 
Anthophyta,  284,  357 
Anthostoma,  343 
Antipodal  nuclei,  287 
Antirrhinum,  304,  367 
Aphanocapsa,  164 
Apiaceae,  372 
Apical  cell,  43 
Apium,  372 
Apocarpous,  292 
Apocynaceae,  366 
Apocynum,  367 
Apogamy,  324 
Aponogetonaceae,  357 
Apopetalous,  305 
Apothccia,  215 
Appendages,  221 
Apple,  307 


Apple,  Blight  bacteria,  169 
Apples,  368 
Aquifoliaceae,  371 
Arabinose,  145 
Araceae,  358 
Arachnoidiscus,  334 
Arales,  295,  358 
Aralia,  372 
Araliaceae,  372 
Araucaria,  279,  356 
Araucariaceae,  278,  356 
Araucarioxyleae,  354 
Arbutin,  149 
Archegone,  110,  243 
Archegonial  gametophytes,  258 
Archespore,  272,  292 
Archidiaceae,  349 
Archiplastideae,  164,  330 
Arctium,  376 
Arctostaphylos,  365 
Arctotidaceae,  375 
Arctotis,  375 
Argemone,  364 
Arisaema,  300,  319,  358 
Aristolochiaceae,  370 
Arnica,  376 
Aromatic  oils,  143 
Artemisia,  376 
Arthonia,  218,  342 
Arthoniaceae,  342 
Arthrocladiaceae,  337 
Arthothelium,  342 
Arum,  358 
Aschersonia,  347 
Asclepiadaceae,  367 
Asclepias,  367 
Ascobolaceae,  342 
Ascobolus,  342 
Ascocorticiaceae,  341 
Ascocorticium,  341 
Ascoidaceae,  344 
Ascophyllum,  337 
Ascosporeae,  211,  339 
Ascospores,  213 
Ascus,  213 

Fungi,  213,  339 
Aseroe,  345 

Asexual  reproduction,  109,  171 
Ash,  324 

Asimina,  274,  361 
Asparagin,  154 


INDEX 


383 


Asparagus,  358 
Aspergillaceae,  344 
Aspergillales,  344,  222 
Aspergillus,  221,  344 
Aspidium,  259 
Asplenium,  259,  353 
Assimilative  processes,  84 
Aster,  376 
Asteraceae,  376 
Asterales,  311,  373 
Asters,  376 
Astrotheliaceae,  343 
Atriplex,  365 
Atropa,  366 
Atropine,  150 
Aulocomniaceae,  350 
Auricularia,  346 
Auriculariaceae,  346 
Aurioulariales,  230,  346 
Austrian  Pine,  282 
Autonomous  movements,  121 
Aiixanometer,  108 
Auxiliary  cells,  208 
Avena,  300,  359 
Aveneae,  359 
Axes  of  flowers,  301 
Axiflorae,  301 

-Apopetalae-Polycarpellatae, 
361 

-Gamopetalae-Dicarpellatae, 
366 

-Gamopetalae-Polycarpellatae, 
365 
Axis  Flowers,  301,  302,  361 

(of  flower),  285 
Azolla,  353 


B 


Baccharis,  376 
Bacillaria,  181 
Bacillariaceae,  334 
Bacillarioideae,  177,  179,  333 
Bacillus,  331 
Bacteria,  166,  331 
Bactoriaroae,  331 
liactcrialcs,  166,  331 
liactcrium,  331 
Balanophoraceac,  371 
Balanopsidaceae,  3()2 
Bald  Cypresses,  278 


lialsamia,  344 
Balsamiaceae,  344,  363 
Bamboo,  297,  359 
Bambusa,  359 
Bambuseae,  359 
Banana,  301 
Bananas,  360 
Bangiaceae,  338 
Bangiales,  338 
Bangioideae,  207.  338 
Banner,  308 
Barberry,  319 
Barbula,  350 
Barley  Smut,  237 
Bartramiaceae,  350 
Basellaceae,  364 
Basidia,  226 

Basidiosporeae,  211,  226,  344 
Basidiospores,  226 
Basidium  Fungi,  226,  344 
Bast  fibers,  33 
Batidaceae,  365 
Batrachospermum,  209,  338 
Battarca,  345 
Bazzania,  349 
Bean,  314 

Family,  309 
Beans,  368 
Bed  straw,  325 
Beeches,  372 
Beetle  Fungi,  339 
Beggiatoa,  331 
Beggiatoaceae,  331 
Begonia,  370 
Begoniaceae,  370 
Begonias,  370 
Bcllis,  376 
Bellworts,  373 
Bennettitaceac,  355 
Bennettitales,  355 
Bcnnettitos,  274 
Bennettitineae,  274,  355 
Benzoic  acid,  141 
Beomyccs,  340 
Berberidaceae,  361 
Berberin,  150 
liergamot  oil,  11 4 
Berries,  326 
Berry,  309 
Beta,  365 
Betula,  372 


384 


INDEX 


Betulaceae,  372 
BicoUateral  bundles,  59 
Bicuculla,  364 
Biddulphiaccae,  334 
Bignonia,  3G7 
Bignoniaceae,  367 
Birches,  372 

Bird-nest  Fungi,  228,  345 
Bixaceae,  363 
Black  Blast,  237 

-dot  Fungi,  239,  348 

Knot,  219 

Molds,  189,  335 

Mosses,  251,  349 

Rust,  233 
Bladder  Algae,  192,  336 

-fern,  259 

Kelp,  201 
Blanc  mange,  209 
Blazing  Stars,  376 
Blue  Greens,  164,  330 

Molds,  222 

-stem  Grasses,  360 
Boehmeria,  362 
Bog  Mosses,  252,  351 
Boletus,  346 
Bombacaceae,  362 
Bonnemaisoniaceae,  339 
Borraginaceae,  366 
Borrago,  366 
Bothrodendraceae,  354 
Botrychium,  352 
Botrydiaceae,  336 
Botrydium,  192,  336 
Botryococcus,  332 
Botrytis,  239,  348 
Boundary  tissue,  46 
Bouteloua,  359 
Bovista,  345 
Brachytheciaceae,  351 
Brake,  259 

Brand-Fungi,  232,  346 
Brassica,  303,  364 
Brassicaceae,  364 
Breathing  pores,  51 
Breeding  of  Plants,  115 
Bremia,  188 
Bridal  Wreath,  307 
Bristle  Mosses,  252,  350 
Brome  Grass,  297 
Bromeliaceae,  360 


Bromus,  297,  359 
Brood  cells,  247 

Masses,  246,  252,  351 
Broom- rapes,  321 
Brown  Algae,  199,  336 

Seaweeds,  201 
Brucine,  150 
BruncUiaceae,  369 
Bruniaceae,  369 
Bryaceae,  252,  350 
Bryales,  251,  349 
Bryophyta,  242,  348 
Bryopsidaceae,  336 
Bryopsidoideae,  185,  336 
Bryopsis,  192,  336 
Bryum,  350 
Buckeyes,  371 
Buckthorns,  371 
Bud,  45 

Budding,  21,  223 
Buellia,  341 
Buelliaceae,  341 
Bulbs,  319 
Bulrush,  300 
Bunt,  237 
Burdock,  325 
Burmanniaceae,  360 
Bursa,  364 
Burseraceae,  363 
Butomaceae,  357 
Buttercup,  286,  361 
Butyl,  142 
Butyric  acid,  140 
Buxaceae,  371 
Buxbaumiaceae,  252,  351 


Cabombaceae,  362 
Cactaoeae,  370 
Cactales,  370 
Cactus,  310,  370 
Cactuses,  370 
Caesalpinia,  308 
Caffeine,  149 
Caladium,  358 
Calamariaceac,  353 
Calamariales,  353 
Calamarineae,  264,  353 
Calamites,  254,  261,  264,  353 
Calamophyta,  261,  353 


INDEX 


385 


Calamus,  358 
Calendula,  375 
Calcndulaccac,  375 
Caliciaceae,  341 
Calicialcs,  341 
(^aliciuni,  341 
Calla,  358 

Lilies,  205 
Callitriehaccae,  303 
Callophyllis,  200,  339 
Callymenia,  200 
Caloplaca,  340 
Caloplaceae,  340 
Caltha,  201 
Calvatia,  228 
Calycanthaceae,  3G1 
Calyceraceae,  373 
Calyciflorae,  302 

-Apopetalae,  368 

-Gamopetalae,  373 
Calymperaceae,  350 
Calyptra,  251 
Calyx,  286 

Cambium,  58,  60,  260,  283 
Camomiles,  376 
Campanula,  373 
Campanulaceae,  373 
Campanulales,  373 
Camphor,  144 
Camphors,  143 
Campsopogonaceae,  338 
Camptosorus,  250 
Camptotrichaceae,  331 
Camptothrix,  331 
Canada  Thistle,  319 
Canal  Cells,  244 
Canary  Grasses,  359 
Cane    Sugar,  17,146 
Canna,  360 
Cannabis,  362 
Cannaceae,  360 
Caoutchouc,  144 
Capparidaceae,  364 
Caprifoliaceae,  373 
Capsicum,  366 
Capsule,  250 

Carbohydrates,  13,  84,  85,  144 
Carbonic  Acid,  85,  139 
Carduaccae,  376 
Carduus,  376 
Carcx,  358 


Caricaceae,  364 
Carnegiea,  370 
Carotin,  155 
Carpels,  286 
Carpinus,  321,  372 
Carpomycetoac.  211,  339 
Carpospores,  206 
Carrot,  315 
Caryocaraceae,  363 
Caryophyllaceae,  364 
Caryophyllales,  364 
Caryopsis,  298 
Cassia,  368 
Cassiaceae,  368 
Castalia,  364 
Castanea,  314,  372 
Castilleia,  367 
Castor  Bean,  305 

oil.  143 
Casuarinaceae,  369 
Catalase,  153 
Catalpa,  367 
Catascopiaceae,  350 
Catkins.  321 
Cat-tails,  357 
Caulerpa,  107 
Caulerpaceae,  336 
Ceanothus,  371 
Cedar-apples,  238 
Cedars,  281 
Cedrus,  281 
Celastraceae,  371 
Celastrales,  370 
Celidiaceae,  342 
Cell,  4 

division,  10 

inclusions,  13 

sap.  17 

wall.  5 
Cellulose.  5 
Celluloses.  147 
Celosia,  365 
Celtis,  362 
Cenangiaceae,  342 
Centrifugal  apparatus,  131 
Centrolepidiaceae,  358 
Centrosomc.  2 
Century  Plant,  320 
Ophalotaceae,  360 
Ceramiaceae,  339 
Ceraniiales,  338 


386 


INDEX 


Ceramium,  339 

Ceratomyces,  339 

Ceratophyllaceae,  362 

Ceratostoinataceae,  343 

Cercidiphyllaceae,  301 

Cercospora,  239,  348 

Cereus,  370 

Ceropegia,  367 

Chaetangiaccae,  338 

Chaetocerotaceae,  334 

Chaetocladiaceae,  335 

Chaetocladium,  335 

Chaetomiaceae,  343 

Chaetophora,  173,  332 

Chaetophoraceae,  332 

Chaetophorales,  332 

Chalazal,  279 

Chamaecyparis,  356 

Chamaerops,  358 
^hamaesiphon,  330 

Chamaesiphonaceae,  330 

Chaptalia,  376 

Chara,  193,  336 
•,'Characeae,  194,  336 

Charales,  193,  336 

Chemistry  of  the  plant,  139 

Chemotaxy,  119 

Chemotropism,  127 

Chenopodiaceae,  365 

Chenopodium,  365 

Cherry,  314,  325 

Chestnut,  314 

Chiodectonaceae,  342 

Chitin,  5,  154 

Chlaenaceae,  362 
ji(fehlamydomonas,  173 

Chlamydosporcs,  184 

Chloranthaceae,  361 

Chlorideae,  359 
,  Chlorococcaceae,  332 
.:^hlorococcum,  171,  332 
'^Chlorophyceae,  170,  332 

Chlorophyll,  11,  155 

Chlorophyllan,  155 

Chloroplasts,  2,  11,  84 

Cholera  bacteria,  169 

Chondromyces,  331 

Chondrus,  208,  339 

Chordariaceae,  337 

Choristocarpaceae,  337 

Christmas  decorations,  267 


^ 


Chromatin,   2 

Chromatium,  331 

Chromoplasts,  2,  12 

Chromosome  number,  110 

Chromosomes   22,  110 

Chroococcaceac,  164,  330 
hroococcus,  164,  330 
hrysanthemums,  376 

Chrysothricaceae,  340 

Chytridiaceae,  336 

Chytridium,  336 

Cichorium,  377 

Cicuta,  372 

Cilia,  118 

Cinchona,  373 

Cineol,  144 

Circaea,  370 

Circinately,  256 

Circumnutation,  123 

Cistaceae,  363 

Citral,  144 

Citric  acid,  141 

CitruUus,  370 

Citrus,  363 

Cladochytriaceae,  335 

Cladonia,  216,  340 

Cladoniaceae,  340 

Cladophora,  185,  334 

Cladophoraceae,  334 

Cladophorales,  334 

Cladosporium,  348 

Cladoxyleae,  354 

Classes,  159 

Classification  of  plants,  157 

Clathraceae,  345 

Clathrus,  345 

Clavaria,  346 

Clavariaceae,  230,  346 

Claviceps,  220,  343 

Claytonia,  323,  364 

Clematis,  361 

Clethraceae,  365 

Climaciaceae,  252,  351 

Climacium,  351 

Climbing  Ferns,  258 

Closed  bundles,  58 
Fungi,  218,  343 
Lichens,  218,  342 

Closteriaceae,  179,  333 

Closterium,  179,  333 

Clover-nodule  bacteria,  169 


INDEX 


387 


Club-Mosses,  267.  354 
Cluster-cups,  233 
Cneoraccae,  363 
Cnicus,  376 
Cocaine,  150 
Coccaceae,  331 
Cocci,  166 

CoccoKonalos,  164,  330 
Coccoloba,  365 
Cochlospermaceac,  363 
Cocklebur,  324 
Coconut,  296,  324 
Cocos,  296,  358 
Codiaceao,  334 
Codiuni,  195,  334 
Cocnobiales,  172,  332 
Coenocytes,  8,  172 
Coenogoniaceae,  340 
Coffea,  373 
Coffees,  373 

Coleochaetaceae,  174,  333 
Coleochaetales,  333 
Coleochaete,  174,  333 
Coleosporiaceae,  347 
Coleosporium,  347 
Coleus,  367 
Collateral  bundles,  58 
Collema,  216,  340 
CoUemataceae,  340 
Collenchyma,  32 
Colletia,  371 
CoUetotrichum,  240,  348 
Colon  bacteria,  169 
Colors  of  flowers,  322 
Columelliaceae,  367 
Combretaceae,  370 
Commelina,  358 
Commelinaceae,  358 
Common  Cycads,  272,  354 

Ferns,  258,  353 

Horsetail.  264 
Companion  cells,  39 
Composites,  312,  373 
Compound  pistil,  295 
Concentric  bundles,  57 
Conceptades.  202 
Conducting  System,  54 
Confervas,  173,  332 
Confervoideae,  171,  173,  332 
Conidia,  ISS 
Conidiophore,  188 


Coniferales,  356 
Conifer  Ancestors,  275,  355 
Coniferin,  148 
Conifers,  277,  355 
Coniine,  150 
Conjugatae,  177,  333 
Conjugate  Algae,  177,  333 
Conjugation,  182 
Connaraceae,  368 
Conocephalus,  349 
Constituents  of  plants,  82 
Convolvulaceac,  366 
Convolvulus,  366 
Coprinus,  345 
Coral  Fungi,  230,  34G 
Corallina,  207,  338 
Corallinaceae,  338 
Corallines,  207 
Cordaitaceae,  355 
Cordaitales,  275,  355 
Cordaites,  275 
Cordaitineae,  355 
Cordieritidaceae,  342 
Cordyceps,  343 
Core  (apple),  308 
Coreopsis,  315 
Coriandrum,  372 
Coriariaceae,  371 
Cork,  67 
Corms,  319 
Cornaceae,  372 
Cornels,  372 
Corn  (Indian),  298 

Smut,  236 
Cornus,  322,  372 
Corolla,  286 
Corsiniaceae,  349 
Corticium,  346 
Corylus,  372 
Corynocarpaceae,  371 
Coscinodiscaceae,  334 
Coscinodiscus,  181,  334 
,   Cosmariaceae,  179,  333 
r^Cosmarium,  179,  333 
Cotinus,  372 
Cotton.  305 

Cotyledons.  268,  282,  293 
Cow  Parsnip,  315 
Crassulaceae,  369 
Crataegus,  313,  368 
Crenothrix,  331 


388 


INDEX 


Crocus,  360 
Cronartium,  347 
Crossosomataceae,  368 
Croton,  363 

oil,  143 
Crotonic  acid,  143 
Crown-gall  bacteria,  169 
Crucibulum,  345 
Crucigenia,  332 
Cryphacaccae,  351 
Cryptoneniialcs,  338 
Crystals,  15 

Cucumber-wilt  bacteria,  169 
Cucumis,  370 
Cucurbita,  305,  370 
Cucurbitaceae,  370 
Cucurbitariaceae,  343 
Culture  solutions,  97 
Cunoniaceae,  369 
Cup  Flowers,  302,  300,  367 

-fungi,  216,  341 
Cuphea,  369 
Cupressaceae,  282,  356 
Cupressus,  356 
Currant,  309 
Cuscuta,  320,  366 
Cushion  Mosses,  252,  349 
Cutin,  155 
Cutleriaceae,  337 
Cutleriales,  337 
Cyanastraceae,  358 
(Cyanophyceae,  330 
Cyathea,  352 
Cyatheaceae,  258,  352 
Cyathus,  345 
Cycadaceae,  354 
Cycadales,  354 
Cycadineae,  272,  354 
Cycadophyta,  271,  354 
Cycads,  271,  354 
Cycas,  273,  354 
Cyclamen,  365 
Cyclanthaceae,  358 
Cyclosporeae,  337 
Cydonia,  313 
Cylindrocapsa,  333 
Cylindrocapsaceae,  333 
Cylindrospermum,  165,  331 
( 'ylindrosporium,  346 
Cymathere,  201 
Cynocrambaceae,  365 


Cynomoriaceae,  370 
Cyperaceae,  298,  358 
Cyperus,  301,  358 
Cypheliaceae,  341 
Cyphelium,  341 
Cypresses,  282,  356 
Cypripedium,  299,  301 
Cyrillaceae,  371 
Cystocarp,  110,  206 
Cytase,  152 
Cytology,  1 
Cytoplasm,  1 
Cyttariaceae,  342 

D 

Dacryomycetaceae,  346 
Dahlias,  320 

Dandelion,  312,  313,  324 
Dasya,  209,  339 
Dasycladaceae,  336 
Dasycladales,  336 
Dasycladus,  336 
Dasyscypha,  342 
Datiscaceae,  370 
Datura,  366 
Daucus,  315,  372 
Dead  nettle,  306 
Death  from  disease,  136 
Death  of  plants,  95 
Delesseria,  339 
Delesseriaceae,  339 
Dematiaceae,  348 
Dematium,  348 
Derbesiaceae,  336 
Dermatocarpaceae,  343 
Dermatogen,  44 
Desmarestiaceae,  337 
Desmidiaceae,  178,  333 
Desmidiales,  333 
Desmidium,  333 
Desmids,  178,  333 
Devil's  aprons,  200 
Dextrose,  145 
Dextro-tartaric  acid,  141 
Dianthus,  300,  364 
Diapensiaceae,  305 
Diaporthe,  343 
Diastase,  153 
Diatomin,  156,  179 
i4Diatoms,  179,  333 


INDEX 


389 


Diatrj-paceae,  343 
Dicaeoina,  347 
Dichacnaceac,  343 
Dichapctalaccao,  363 
Dichoniyces.  339 
Dicksonia,  352 
Diclinous,  29G 

Dicotylcdoneae,  294,  301,  361 
-Axiflorae,  361 
-Calyciflorap,  367 
Dicotyledons,  301,  361 
Dicranaceae,  252,  349 
Dictyophora,  345 
Dictyosiphonaceae,  337 
VDictyota,  337 
'^Dictyotaceae,  337 
Dictyotineae,  337 
Digitalis,  306 
Dilleniaceac,  362 
Dimorphism,  323 
Dioecious,  273 
Dioon,  355 
Dioscoreaceae,  360 
Diphtheria  bacteria,  169 
Diploid,  24,  110 
Diploschistaceae,  340 
Dipsacaceae,  373 
Dipterocarpaceae,  363 
Dirinaceae,  342 
Disaccharids,  146 
Disceliaceae,  350 
Discella,  348 
Discolichenes,  214,  340 
Diseases  of  Plants,  133 
Disc  Algae,  174 
flowers,  312 
Lichens,  214,  340 
Division  of  cells,  19 
Dodder,  320,  321 
Dodecatheon,  365 
Dogwood,  322 
Dothidia,  343 
Dothidiaceae,  343 
Downy  Mildews,  187,  335 
Draparnaldia,   173,    332 
Drci)anophyllaceae,  350 
Droseraceae,  369 
Duchesnea,  291 
Duckweeds,  358 
Dulcite,  142 
Dumontiaciae,  338 


Durvillaea,  337 
Durvillaeaceae,  337 
Dutch  Rush,  264 
Dwarf  males,  174 

E 

Ears,  298 

Ear  Fungi,  230.  346 
Earth  Stars,  231 
Ebenaceac,  366 
Ebenales,  365 
Echinocactus,  370 
Ectocarpaceae,  337 
Ectocarpales,  337 
Ji^ctocarpus,  200,  337 
Ectolechiaceae,  340 
Egg,  110,  174 
Egregia,  201,  337 
Elachistaceae,  337 
Elaeagnaceae,  371 
Elaeocarpaceae,  362 
Elaphomycetaceae,  34 
Elaters,  245,  263 
Elatinaceae,  364 
Elder,  315 
Elephantopus,  376 
Elms,  362 
Embryo,  280 
Emergencies,  51 
Empetraceae,  371 
Emulsin,  153 
Encalypta,  350 
Encoeliaceae,  337 
Endocarpon,  218 
Endomyces,  341 
Endomycetaceae,  341 
Endosperm,  274.  284,  288 

nucleus,  288 
Endospores,  166 
Energy,  90 

supply  of,  91 
Enteromorpha,  174,  332 
Entodontaceac,  351 
Entomophilous,  321 
Entomophily,  323 
Entomophthora,  191,  336 
Entomophthoraceae,  191,  336 
Entomojihthoralcs,  336 
Entyloma,  347 
Enzymes,  152 
Epacridacoae,  3(>5 


390 


INDEX 


Ephebaceae,  340 
Ephebe,  216 
Ephedra,  275,  355 
Ephedraceae,  355 
Ephemeral  Mosses,  252' 
Ephemerum,  252,  350 
Epicoccum,  348 
Epidermal  System,  47 
Epidermis,  48 
Epigloea,  342 
Epiglueaceae,  342 
Epilobium,  370 
Epiplasm,  24 
Equisetaceae,  263,  353 
Equisetales,  353 
Equisetineae,  262.  353 
Equisetum,  262,  353 
Eremascus,  341 
Ergot,  220 
Erica,  365 
Ericaceae,  365 
Ericales,  365 
Erigeron,  376 
Eriocaulonaceae,  358 
Eriogonum,  365 
Erodium,  362 
Erpodiaceae,  351 
Erysiphaceae,  220,  344 
Erysiphe,  220,  225,  344 
Erythronium,  300,  357 
Erythroxylaceae,  363 
Eschscholtzia,  364 
Ethyl  alcohol,  141 
Euastrum,  179 
Eubacteria,  331 
Eucalyptol,  144 
Eucalyptus,  370 

oil,  144 
Eucomiaceae,  369 
Eucryphiaceae,  363 
Eugenia,  370 
Euodiaceae,  334 
Eupatoriaceae,  376 
Eupatorium,  376 
Euphorbia,  322,  363 
Euphorbiaceae,  363 
Eupodiscaceae,  334 
Eupodiscales,  181,  333 
Eupodiscus,  334 
Eusporangiatae,  257,  352 
Eustoma,  366 


Evaporation  of  water,  74,  75 
Evening  Primrose,  309,  370 
Everlastings,  375 
Evolution,  160 

of  Anthophyta,  316 
Evolvulus,  366 
Excipula,  348 
Excipulaceae,  348 
Exidia,  346 
Exoascaceae,  341 
Exoascalcs,  218,  341 
Exoascus,  218,  341 
Exobasidiaceae,  346 
Exobasidiales,  231,  346 


Fabaceae,  368 

Fabroniaceae,  351 

Fagaceae,  372 

Fagopyrum,  365 

Fagus,  372 

False  Hemlocks,  281 
Sunflowers,  375 
tissues,  28 
Tubers,  227,  344 

Families,  159 

Fats,  14,  142 

Fatty  oils,  142 

Fermentation,  223 

Ferns,  254 

Fertilization  of  the  egg,  273 

Ferula,  372 

Fescue  Grasses,  359 

Festuceae,  359 

Fibrous  tissue,  33 

Fibrovascular  system,  47 

Ficus,  362 

Figs,  362 

Filament,  292 

Filicales,  258,  352 

Filix,  259 

Filmy  Ferns,  258,  352 

Firs,  281 

First  stom'ata,  245 

Fissidentaceae,  350 

Fission,  20 

Flacourtiaceae,  362 

Flagella,  118 

Flagellariaceae,  358 

Flagellata,  172 


INDEX 


391 


riat  Diatoms,  181,  334 

Kelps,  200 
Florideae,  207,  338 
Flower,  274,  285 

axes,  301 
Flowering   Plant  Ancestors,  274, 
355 
Plants,  274,  284,  357 
"Flower"  of  Mosses,  250 
Fly  Fungi.  33G 
Foeniculum,  372 
Fomes,  230,  346 
Fontinalaceae,  252,  351 
Forget-me-nots,  3G6 
Formaldehyde,  85,  153 
Formation  of  New  Cells,  19 
Formic  Acid,  140 
Fossombronia,  349 
Fouquieraceae,  3G4 
Fragaria,  289,  306,  368 
Fragiiariaceae,  334 
Frankeniaceae,  364 
Fraxinus,  366 
Free  veins,  257 
Freezing  of  plants,  96 
Froelichia,  365 
Fructose,  18,  145 
Fruit,  288 

-spores,  175 
Sugar,  145 
FruUania,  349 
Fucaceae,  337 
Fucales,  201,  337 
Fuchsia,  370 
^^ucus,  201,  337 
'  Funaria,  250,  350 
Funariaceae,  252,  350 
Fungi,  179,  211 

Imperfecti,  213,  347 
Fungus  cellulose,  5,  154 

sugar,  146 
Fusarium,  34S 
Fusel  oil,  142 
Fusidadium,  239,  348 


Gaillardia,  375 
Galactose,  145 
Galium.  373 
Gall-fungi,  172 


Gallic  acid,  141 

Gallotannic  acid,  141 

Gametangia,  200 

Gametes,  109 

Gametophyte,  110,  242 

Gamopetalous.  303 

Gamosepaly,  304 

Garden  Currant,  309 

Gaura,  370 

Gazania,  375 

Gazanias,  375 

Geaster,  231,  345 

Geissolomataceae,  371 

Gelidiaceae,  338 

Gemmae,  246 

Genera,  158 

Generation,  171 

Genicularia,  333 

Gentiana,  366 

Gentianaceae,  366 

Gentianales,  366 

Geoglossaceae,  342 

Geoglossum,  342 

Geologic  time,  161,  162 
Georgiaceae,  351 
Geotropism,  125 
Geraniaceae,  362 
Geraniales,  362 
Geranium,  302,  362 
Geraniums,  362 
Gerardia,  367 

Germination  of  seed,  281,  288 
Gesneraceae,  367 
Geum.  291 
Giant  Kelp,  201 

Puff-I)all.  228 
Gigartina.  339 
Gigartinaceae,  339 
Gigartinales,  339 
Gilia,  366 
Gills,  230 
Ginkgo,  275,  355 
Ginkgoaceae,  355 
Ginkgoales.  275,  355 
Ginsengs,  ',i7'2 
Girdle.  ISO 
Gladiolus.  319,  360 
Glaucocystaceae,  167,  332 
Glaucocystales,  167,  332 
Glaucocystis,  167,  332 
Glcba,  228 


392 


INDEX 


Gleditsia,  368 
Gleicheniaceae,  352 
Globulariaceae,  307 
'Gloeocapsa,  164,  330 
Gloeosporium,  239,  348 
Gloiosiphoniaccae,  338 
Glucose,  18,  85,  145 
Glucosides,  148 
Glume,  297 
Glycerine,  142 
Glycogen,  147 
Glycollic  acid,  140 
Gnaphaliuni,  376 
Gnetaceue,  355 
Gnetales,  275,  355 
Gnetum,  275,  355 
Gnomoniaceae,  343 
Golden  Fern,  258 
Gomortegaceae,  361 
Gonatonema,  333 
Gonidia,  214 
Gonium,  332 
Gonystylaceae,  362 
Goodeniaceae,  373 
Gooseberries,  314,  369 
Gordonia,  363 
Gossypium,  305,  362 
Grain  (of  grass),  298 
Graminales,  297,  358 
Gramma  Grasses,  359 
Grammatophora,  334 
Grapes,  326,  371 
Grape  Sugar,  18,  145 
Graphidaceae,  342 
Graphidales,  218,  342 
Graphina,  342 
Graphis,  218,  342 
Graphium,  348 
Grasses,  297,  359 
Grasshopper  Fungus,  191 
Grateloupiaceae,  338 
Gray  Mosses,  214 
Great  Horsetail,  264 

Liverwort,  246,  349 
Green  Felts,  185,  334 

Slimes,  171,  332 
Grimmiaceae,  350 
Grinnellia,  209,  339 
Grippe  bacteria,  169 
Grossulariaceae,  369 
Ground  Pines,  267,  354 


Groundsels,  376 
Growing  point,  45 
Growth,  104 

movements,  122 

rings,  62 
Grubbiaceae,  371 
Gulfweeds,  201 
Gum  canals,  66 
Gutta  Percha,  144 
Guttation,  77 
Guttiferaceae,  363 
Guttiferales,  363 
Gyalectaceae,  340 
Gymnoascaceae,  344 
Gj^mnoascus,  344 
Gymnocladus,  368 
Gymnogramme,  258 
Gymnospermous,  330 
Gymnosporangium,  235 
Gyrophoraceae,  340 

H 

Habitat,  320 
Hadromal,  154 
Haematococcus,    173 
Haemodoraceao,  360 
Hair-cap  Mosses,  252 
Hair  Caps,  351 
Hairs,  49 
Halicystis,  336 
Halidrys,  337 
Halimeda,  195 
Halophytes,  320 
Halorrhagidaceae,  370 
Hamamelidaceae,  369 
Haploid,  24,  110 
Haplosiphon,  165 
Hard  Puff-balls,  344 

Red  Seaweeds,  338 
Haustoria,  188 
Hawkweed,  324 
Hawthorn,  313 
Heartwood,  62 
Heaths,  365 
Hedera,  372 
Hedwigiaceae,  351 
Heleniaceae,  375 
Helenium,  375 
Helianthus,  311,  312,  375 
Hclianthaceae,  375 


INDEX 


393 


Helichrysuni,  376 

Helicophyllaceae,  351 

Holiotropiuni,  366 

llelinintliooladiaceae,  338 

llelotiaeoao,  342 

Hclotiuni,  342 

Helvella.  342 

Helvellaccae,  342 

Hclvellalcs,  217,  342 

Ilelvellas,  342 

Hcniiascales.  223,  344 

Hemlocks,  281 

Hepatica,  291 

Hepaticac,  244,  348 

Heppiaceae.  340 

Heptane,  153 

Heracleum,  315,  372 

Herbarium  Mold,  221 

Hernandiaceae,  371 

Herposteiraceae,  333 

Herposteiron,  333 

Hesperidin,  149 

Heterocysts,  165 

Heteroecism,  234 

Heterogametes,  174 

Heterogamous,  110 

Heterospores,  255 

Heterothallic,  191 

Heuchera,  369 

Hibiscus,  362 

Hickory,  314 

Hicoria,  314,  372 

Hieracium,  377 

Higher  Fungi,  211,  330 
Lycopods,  267,  354 
Red  Seaweeds,  339 
Tube  Algae,  336 

Highest  plant,  313 

Himanthalia,  337 

Himanthaliaceae,  337,  371 

Hippocrateaceae,  371 

Hippuridaceae,  370 

Histology.  27,  43 

Hollyhock,  305 

Holophytes,  88 

Holoplastideae,  164,  167,  332 

Homothallic.  197 

Honey  Locust,  319 

Honeysuckle,  311,  373 

Hookeriaceae,  351 

Hormogonales,  165,  330 


Hormogones,  163 
Hornworts,  245,  349 
Horsemint,  306 
Horsetails,  262,  353 
Houstonia,  373 
Hoya,  367 
Humiriaceae,  363 
Humpback  Mosses,  252,  351 
Humulus,  362 
Husks,  298 
Hyacinth,  320 
Hyaloriaceae,  346 
Hyalothcca,  333 
Hydnaccae,  230,  346 
Hydnoraceae,  370 
Hydnum,  346 
Hydrales,  360 
Hydrangea,  369 
Hydrangeaceae,  360 
Hydrocharitaceae,  360 
Hydrochinin,  150 
Hydrochloric  acid,  139 
Hydrocyanic  acid,  148 
Hydrodictyaceae,  332 
Hydrodictyon,  172,  332 
Hydrophyllaceae,  366 
Hydrophyllum,  366 
Hydrophytes,  320 
Hydrostachydaceae,  364 
Hygroscopic  movements,  116 
Hymenium,  213,  226 
Hymenogastraceae,  344 
Hymenogastrales,  227,  344 
Hymenophyllaceae.   258,  352 
Hymenophyllum,  352 
Hyoscyamine,  150 
Hyperplasy,  134 
Hypertrophy,  134 
Hyphae,  189 
Hypnaceae,  252,  351 
Hypnodendraceae,  351 
Hypnum,  351 
Hypochnaceac,  34G 
Hypocreaceae,  343 
Hypoderniataceae,  343 
Hypoplasy,  134 
Hypopterygiaccae,  351 
Hyijoxis,  360 
Hy  poxy  Ion,  343 
Hysterangiuni,  344 
Hysteriaceae,  343 


394 


INDEX 


Hysteriales,  218,  343 
Hysterium,  343 
Hysterographiuni,  218,  343 
Hysterophytes,  88 


Icacinaceae,  371 
Immunity  to  diseases,  137 
Impatiens,  363 
Imperfect  Fungi,  347 
Imperfecti  (Fungi),  213 
Increased  parental  care,  110 
Indian  Corn,  298 
Smut,  236 

Pipes,  321 
Indusium,  273 
Inferior  ovary,  298 
Influenza  bacteria,  169 
Inheritable  variations,  113 
Inorganic  Acids,  139 

Salts,  139 
Inula,  376 
Inulaceae,  375 
Inulin,  18,  147 
Insect  Fungi,  191 
Insectivorous  Plants,  362 
Integument,  273 
Intercellular  spaces,  65 
Interzones,  180 
Invertase,  152 
Involucre,  311,  312 
Ipomoea,  366 
Iridaceae,  360 
Iridales,  298,  360 
Iris,  299,  360 
Irish  Moss,  208 
Ironweeds,  376 
Irpex,  346 

Irregular  flowers,  303,  322 
Isaria,  348 
Isobutyl,  142 

carbinol,  142 
Isobutyric  acid,  140 
Isoetaceae,  352 
Isoetales,  258,  352 
Isoetes,  260,  352 
Isogametes,  171 
Isogamous,  110 
Isospores,  255 
Ithyphallus,  345 


Jambosa,  370 
Jasminum,  366 
Jelly  Fungi,  230,  346 
Jelly  Lichens,  216 
Jerusalem  Artichoke,  320 
Joint-firs,  275,  355 
Juglandaceae,  372 
Juglans,  310,  372 
Julianaceae,  372 
Juncaceae,  358 
Juncus,  358 
Jungermannia,  247 
Jungermanniaceae,  247,  349 
Jungermanniales,  247,  349 
Juniperaceae,  282,  356 
Junipers,  282 
Juniperus,  356 

K 

Kalmia,  365 

Karyokinesis,  20 

Keel,  308 

Kelps,  200,  336 

Kernel  (of  grass),  298 

Key  to  families  of  Asterales,  374 

to  the  Phyla,  328 
Kinoplasm,  22 
Klinostat,  131 
Knot-grass,  326 
Koeberliniaceae,  364 
Koelreuteria,  371 
Kuhnia,  376 


Laboratory  suggestions,  8 
Laboulbenia,  339 
Laboulbeniaceae,  339 
Laboulbeniales,  339 
Lachnea,  342 
Lacinaria,  376 
Lacistemaceae,  361 
Lactic  acid,  141 
Lactoridaceae,  361 
Lactose,  146 
Lactuca,  315,  377 
Lactucaceae,  377 
Lady's  Slipper,  301 


INDEX 


395 


Lagonaria,  370 
Lamb's  (luarters,  326 
Lainiarcao,  307 
Lainialos,  307 
Laininaria,  200,  337 
Laminariaooae,  200,  337 
Lamium,  30G 
Laniprothaninus,  336 
Land  Ferns,  2o2,  258 

Habit,  242 
Lantana,  367 
Larches,  281 
Lardizal)alaceae,  301 
Lar^e  Bladder  Algae,  331 
Larix,  281,  350 
Lasiosphaeria,  343 
Latex,  39 
Lathyrus,  314 
Laticiferous  tissue,  39 
Lauraceae,  301 
Lavandula,  307 
Lavender  oil,  144 
Laver,  207 
Leafy  Kelp,  201 
Leathery  fungi,  230 
Leaves,  247,  249,  255 
Lecanactidaceae,  340 
Lecanora,  340 
Lecanoraccae,  340 
Lccidiaceae,  340 
Lccythidaceae,  369 
Legume,  309 
Leitneriaceae,  361 
Lejolisia,  339 
Lenianeaceae,  338 
Lenibophyllaceae,  351 
Lemma,  297 
Lemna,  358 
Lemnaceae,  358 
Lennoaceae,  305 
Lentibulariaceae,  367 
Lenticels,  68 
Leontodon.  312,  377 
Lepidodendraceae,  354 
Lepidodcndrales,  269,  354 
Lepidodendrids.  269 
Lopidodcndriiieae,  267,  354 
Lepidodcndron,  269 
Lepidnphyta,  266,  354 
Leptodon,  351 
Leptogium,  210,  340 


Leptosporangiatae,  258,  352 

Leptostomataceae,  350 

Leptostroma,  347 

Lcptostromataceae,  347 

Leptothyrium,  347 

Lepyrodontaceae,  351 

Leskea,  351 

Leskeaceae,  351 

Lessonia,  201 

Lettuces,  377 

Leucobryaceae,  252,  349 

Lcucodontaceae,  351 

Leucomiaceae,  351 

Leucoplasts,  2,  12 

Levulose,  145 

Libocedrus,  356 

Lichens,  214 

Lichinaceae,  340 

Light,  106 

L'gnin,  5,  154 

Ligulate  flowers,  312 

Lilac  Mildew,  225 

Liliaceae,  357 

Liliales,  295,  357 

Lilies,  295,  357 

Lilium,  295,  357 

Limnanthaceae,  363 

Limoncne,  144 

Limonia,  303 

Linaceae,  303 

Linalool,  144 

Lindens,  302 

Linin,  2 

Linnaea,  373 

Linoleic  acid,  143 

Linseed  oil,  143 

Lipase,  153 

Lip  (of  orchids),  301 

Lippia,  307 

Liriodendron,  301 

Lithospermuni,  306 

Little  Bladder  Algae,  336 

Cup-fungi,  341 

Tubers.  221,  344 
Liver  starch,  147 
Liverworts,  244,  348 
Loasa.  370 
Loasaccae,  370 
Loasales,  370 
Lobaria.  340 
Lobelia,  373 


396 


INDEX 


Locomotion  of  cells,  118 

Lodicule,  297 

Loganiaceae,  366 

Lonicera,  311,  373 

Lophiostomataceae,  343 

Lophosia,  349 

Loranthaceac,  371 

Loranthus,  371 

Lotuses,  361 

Lower  Fungi,  186,  335 
Lycopods,  267,  354 
Red  Seaweeds,  338 
Tube  Algae,  334 

Lupinin,  150 

Lupinus,  369 

Lychnis,  303,  364 

Lycoperdaceae,  228,  345 

Lycoperdales,  227,  345 

Lycoperdon,  345 

Lycopodiaceae,  267,  354 

Lycopodiales,  354 

Lycopodineae,  267,  354 

Lycopodium,  354 

Lycopods,  254,  266,  354 

Lyginopterideae,  354 

Lygodium,  258 

Lyngbya,  165,  330 

Lythraceae,  369 

Lythrum,  369 

M 

Macomitrium,  350 
Macrocystis,  201,  337 
Macrosporium,  348 
Macrozamia,  355 
Magnolia,  274,  291,  302,  361 
Magnoliaceae,  361 
Maidenhair  Fern, 259 

Trees,  275,  355 
Maize,  298 

Grasses,  360 
Malaceae,  368 
Malaleuca,  370 
Malesherbiaceae,  363 
Malic  acid,  141 
Mallow,  302 
Mallows,  362 
Malpighiaceae,  363 
Malus,  307,  368 
Malva,  302,  362 
Malvaceae,  362 


Malvales,  362 
Maltose,  146 
Malt  Sugar,  146 
Mangifcra,  372 
Manihot,  363 
Manna  Ash,  146 
Manncotctrose,  146 
Mannitc,  142 
Mannose,  145 
Maples,  371 
Maiantaceae,  360 
Marattia,  352 
Marattiaceae,  352 
Marattiales,  258,  352 
Marattias,  258,  352 
Marcgraviaoeae,  363 
Marchantia,  246,  349 
Marchantiaceae,  349 
Marchantiales,  349 
Marigolds,  375 
Marsilia,  259,  353 
Marsiliaceae,  353 
Marsiliales,  259,  353 
Martyniaceae,  367 
Massariaceae,  343 
Matoniaceae,  352 
Mayaceae,  358 
Maydeae,  360 
Measurements,  9 
Medicago,  369 
Medullary  rays,  61,  283 
Medullosae,  354 
Meeseaceae,  350 
Megagametophytes,  258 
Megasporangia,  268 
Megaspores,  256,  268 
Melampsora,  235,  347 
Melanconiaceae,  348 
Melanconiales,  239,  348 
Melanconidiaceae,  343 
Melanconium,  239,  348 
Mclastomataceae,  369 
Meliaceae,  363 
Melianthaceae,  371 
Melocactus,  370 
Melogrammataceae,  343 
Melons,  370 
Melosira,  181 
Mendel,  112 
Menisperniaceae,  361 
Mentha,  367 


INDEX 


397 


Menthol,  144 
Mentzelia,  370 
Menyanthes,  300 
Meridionacoac,  334 

tierismopedia,  104,  330 
leristeni,  29 
Mertonsia,  300 
Mesocarpacoao,  333 
Mesophyll,  202 
Mcsophytes,  320 
Methane,  153 
Methyl  alcohol,  141 
Methylamine,  153 
Metzgeria,  247,  340 
Metzgeriaccac,  247,  340 
Micrasterias,  170,  333 
Micrococcus,  331 
Microcolevis,  105 
Microgametophytes,  258 
Micropylar  end,  287 
Micropyle,  273 
Microsphaera,  225,  344 
Microspora,  332 
Microsporaceae,  332 
Microsporales,  332 
Microsporangia,  208 
Microspores,  250,  208 
Microthamniaceae,  332 
Microthamnion,  332 
Microthyriaceae,  344 
Mildews,  220,  343 
Milk  Sugar,  140 

tissue,  30 
Milkweeds,  307 
Millon's  reagent,  0 
Mimosa,  308 
Mimosaceae,  308 
Mimulus,  307 
Mints,  307 
Mitchella.  373 
Mitella,  300 
Mitosis,  20 
Mitrula,  342 
Mitteniaceae,  350 
Mniaceae,  252,  350 
Milium,  350 
Modern  Ferns,  25S.  352 

Pines,  270,  35(i 
Molds.  230,  348 
Mollisinceae,  342 
Momordica,  370 


Monarda,  300 
Monilia,  230,  348 
Moniliales,  230,  348 
Monimiaceae,  301 
Mon()l)lei)haridales,  335 
Monoblopharis,  335 
Monocotyledoneae,  204,  205,  357 

-Epigynae,  300 

-Hypogynae,  357 
Monocotyledons,  205,  357 
Monosaccharids,  145 
Monospores,  200 
Monostroma,  173 
Monotropaceae,  321 
Moraceae,  302 
Morchella,  217,  342 
Morels,  217 
Moringaceae,  304 
Moriola,  342 
Moriolaceae,  342 
Morning  Glories,  320,  321,  306 
Morphine,  150 
Mortierella,  335 
Mortierellaceae,  335 
Morus,  302 
Mosses,  248,  349 
Mossworts,  242,  348 
Mougeotia,  333 
Movements,  116 
Mucedinaceae,  348 
Mucor,  180,  335 
Mucoraceae,  ISO,  335 
Mucorales,  335 
Musa,  301,  300 
Musaceae,  300 
Musci,  244,  349 
Mushroom,  218,  229 

Spawn,  229 
Mustard,  303,  304 
Mutations,  114 
Mutinus,  345 
Mutisia,  370 
Mutisiaceae,  376 
Mycelium,  180 
Mycocalicium,  341 
Mycoporaccae,  343 
Mycosphaerellaceae,  343 
Myoporaceae,  307 
Myosotis,  300 
Myosurus,  201.  301 
Myricaccae,  372 


398 


INDEX 


Myriothamnaccae,  3G9 
Myriotrichiaceae,  337 
Myristicaceae,  3G1 
Myrsinaceae,  3G5 
Myrtaceae,  3G9 
Myrtales,  3G9 
Myrtles,  3G9 
Myrtus,  370 
Myxobacteriaceae,  331 
Myxophyceae,  1G3,  330 
Myzodendraceae,  371 

N 

Naiadaceae,  358 
Names  of  plants,  159 
Narcissus,  3G0 
Nastic  movements,  128 
Natural  Selection,  113 
Navicula,  334 
Naviculaceae,  334 
Naviculales,  334 
Neckera,  351 
Neckeraceae,  351 
Nectar  of  flowers,  322 
Nectria,  343 
Nectrioidaceae,  347 
Neluinbaceae,  361 
Nelumbo,  361 
Nemalion,  207,  338 
Nemalionales,  338 
Nemastomaceae,  338 
Nematocaceae,  351 
Nepenthaceae,  362 
Nepeta,  367 
Nephrodium,  353 
Nereocystis,  201,  337 
Nerium,  367 
Netted-veined,  301 
Nettles,  362 

New  Cells,  formation  of,  19 
Nicotiana,  306,  366 
Nicotine,  150 
Nidularia,  345 
Nidulariaceae,  345 
Nidulariales,  228,  345 
Nightshades,  366 
Nigredo,  347 
Nitella,  194,  336 
Nitellaceae,  194,  336 
Nitophyllum,  209,  339 


Nitric  acid,  139 
Nolanaceae,  366 
i^ostoc,  165,  331 
^Nostocaceae,  165,  331 
Nucleus,  1 

Number  of  plants,  157 
Numerical  data,  327 
Nutation,  123 
Nutrition,  71 
Nutritive  tissues,  65 
Nux  vomica,  150 
Nyctaginaceae,  365 
Nymphaea,  364 
Nymphaeaceae,  364 
Nyssa,  372 


Oak,  310 

Oat  Grasses,  359 

Smut,  237 
Ochnaceae,  363 
Octaviana,  344 
Odors  of  flowers,  322 
Oedogoniaceae,  174,  333 
,:yOedogonium,  174,  333 
'Oedopodiaceae,  350 
Oenothera,  309,  370 
Oenotheraceae,  370 
Oidium,  348 
Oils,  14 
Olacaceae,  371 
Old  Calamites,  264,  353 

-fashioned  Ferns,  257,  352 

Pines,  278,  356 
Olea,  366 
Oleaceae,  366 
Oleic  acid,  143 
Olein,  143 
Oliniaceae,  371 
Olives,  366 
Olpidium,  332 
Onion,  320 
Onoclea,  259 
Onygenaceae,  34 
Oogones,  174 
Oospora,  348 
Opegrapha,  342 
Open  bundles,  59 
Operculum,  252 
Ophiogloss^kceae,  352 


INDEX 


399 


Ophioglossales,  257,  352 
Ophioglossuni,  352 
Opiliaccae,  371 
Opposite  leaves,  292 
Opuntia,  310,  370 
Orchidaceae,  3G0 
Orchidales,  299,  360 
Orchids,  299,  3G0 
Orchis,  299,  3G1 
Orders,  159 
Oreodoxa,  358 
Organic  Acids,  140 
Origin  of  Phyla,  161 

of  Zygophyceae,  181 
Orobanchaceae,  321,  307 
Orthotrichaceae,  350 
Orthotrichum,  350 
Oryza,  359 
Oryzeae,  359 
Oscillatoria,  165,  330 
Oscillatoriaceae,  165,  330 
Osmosis,  72 
Osmunda,  352 
Osmundaceae,  352 
Ostrich-fern,  259 
Ostropaceae,  343 
Ostrya,  372 
Ovary,  286,  292 
Ovulate,  275 
Ovule,  273 
Oxalic  acid,  141 
Oxalidaceae,  362 
Oxalis,  326,  362 
Oxidases,  153 


Padina,  337 
Palea,  297 
Palct,  297 
Palisade  tissue,  292 
Palmaceae,  358 
Palmales,  296,  358 
Palmatin,  143 
Palmcllales,  171,  332 
Palmettos,  300 
Palmitic  acid.  140,  143 
Palms,  296,  358 
Panax,  372 
Pandanaceae,  357 
:::4^andorina,  172,  332 


Paniceae,  359 

Panic  Grasses,  359 

Panicum,  359 

Pannariaceae,  340 

Pansy,  306 

Papaver,  364 

Papaveraceae,  364 

Papaws,  361 

Pappus,  312 

J»arallel  veined,  295 
VJaraphyses,  203,  215 
""l^arasitic  habit,  320 

Paratheliaceae,  343 

Paratonic  movements,  123 

Parenchyma,  29 

Parental  care,  110 

Parietal  placentae,  303 

Parkeriaceae,  352 

Parmelia,  216,  340 

Parmeliaceae,  340 

Paronj^chia,  364 

Parsleys,  372 

Parsnip,  311 

Parthenocissus,  371 

Parthenogenesis,  324 

Passage  of  Water,  73 

Passiflora,  364 

Passifioraceae,  363 

Passion  Flowers,  363 

Pastinaca,  311,  372 

Patellariaceae,  342 

Path  of  the  Water,  75 

Pathology,  133 

Pea,  305,  308 

Peach,  314 

Pear,  313 

blight  bacteria,  169 

Peat-mosses,  251,  349 

Pectase,  153 

Pectose,  5 

Pedaliaceae,  367 
'^l5*ediastrum,  172 

Pedicularis,  367 

Peireskia,  370 

Pelargonium,  306,  362 

Pellia,  349 

Peltigcra,  340 

Pcltigcraceae,  340 

Penaeaceae,  371 

Pcnicillium,  222,  344 

Penicillus,  195,  334 


400 


INDEX 


renium,  333 
Pentaphyllaccao,  371 
Pentsteinon,  306 
Peppermint  oil,  l-l-i 
Pepsins,  153 
Perianth,  274,  284 
Peribleni,  44 
Pericarp,  175,  208 
Peridiuni,  228 
Perisporiaoeae,  344 
Perisporiales,  220,  343 
Peristome,  252 
Peritheeia,  215 
Peronospora,  188,  335 
Peronosporaceae,  187,  335 
Pcronosporales,  335 
Peroxidases,  153 
Perseite,  142 
Pertusaria,  340 
Pertusariaceae,  340 
Pestalozzia,  348 
Petals,  286 
Petticoat  Mosses,  252 
Petunia,  304,  366 
Peziza,  216,  342 
Pezizaceae,  342 
Pezizales,  216,  341 
Phacelia,  366 
Phacidiaceae,  341 
Phacidiales,  341 
Phacidium,  341 
Phaeophyceae,  199,  366 
Phaeosporeae,  336 
Phalarideae,  359 
Phalaris,  359 
Phallaceae,  345 
Phallales,  228,  345 
Phascum,  350 
Phaseolus,  314,  369 
Phellonic  acid,  155 
Philadelphus,  369 
Philydraceae,  358 
Phloem,  55 
Phloeonic  acid,  155 
Phlox,  304,  366 
Phoenix,  358 
Phoradendron,  371 
Phosphoric  acid,  139 
Photonasty,  124 
Photosynthesis,  84 
Phototaxy,  119 


Phototropism,  124 
Phragmidium,  235,  347 
Phrymaceae,  367 
Phycobarteriaccae,  331 
Phycocyanin,  156,  163,  205 
Phycoeryt.hrin,  156,  205 
Phycomyceteae,  185,  335 
Phycophaein,  156,   199 
Phyla.  159,  327 
Phylogeny,  114,  157 
Phylogeny  of  Fungi,  240 
Phyllachora,  343 
Phyllactinia,  225 
Phyllocladaceae,  356 
Phyllocladus,  356 
Phyllopsoraceae,  340 
Phyllopyreniaceae,  343 
Phyllosiphon,  334 
Phyllosiphonaceae,  334 
Phyllosticta,  239,  347 
Physalis,  366 
Physcia,  216,  341 
Physciaceae,  341 
Physcomitrium,  350 
"Physiological  Diseases,"  134 
Physiology,  71 
Physma,  340 
Phytolaccaceae,  364 
Phytophthora,  188,  335 
Picea,  281,  356 
Pigments,  155 
Pigweeds,  326 
Pilacraceae,  346 
Pilobolus,  335 
Pilocarpaceae,  340 
Pilotrichaceae,  351 
Pilularia,  353 
Pimenta,  370 
Pinene,  144 
Pines,  281,  356 
Pinks,  303,  364 
Pinoideae,  355 
Pinus,  279,  281,  356 
Piperaceae,  361 
Piperin,  149 

Piptocephalidaceae,  335 
Piptocephalis,  335 
Pirolaceae,  365 
Pirus,  313,  368 
Pistillaria,  346 
Pistils,  284 


INDEX 


401 


Pisuni,  305.  308,  309 
Pithophora,  334 
Pitted  vessels,  36 
Pittosporaccue,  369 
Planera,  302 
Plant  Breeding,  115 

Cell.  4 
Plantaginaceae,  365 
Plantago,  323,  365 
Plantains.  365 
Plasmolysis,  72 
Plasmopara,  187,  335 
Plasticity  of  Plant  body,  319 
Plastids,  2,  10 
Platanaceae,  369 
Platanthera,  361 
Platanus,  369 
Pleosporaceae,  343 
Plerome,  44 
Pleurocarpi,  252,  351 
Pleuromoiaceae,  354 
Pleurophascaceae,  351 
Plocamiuni,  209,  339 
Plowrightia,  219,  343 
Plum,  308 

Plumbaginaceae,  365 
Plum-pocket  Fungus,  218 
Plums,  368 
Plumule,  305 
Poa,  300 

Poaccae,  297,  359 
Pocket  Fungi,  341 
Podaxaceae,  345 
Podaxon,  345 
Podocarpaceae,  356 
Podocarpus,  356 
Podosphaera,  225,  344 
Podostemonaceae,  364 
Pogonatuni,  351 
Poisons,  96 
Polar  nuclei,  287 
Polemoniaceae,  366 
Polemonialos,  306 
Polemonium,  366 
Pollen,  273 

-cells,  284 

-sacs,  286 

tube,  279,  287 
Pollination,  280,  321 
Polygalaceae,  363 
Polygonaceae,  365 


Polygonum.  305 
PolypodiacM'ac.  258,  353 
Polypodium,  258,  353 
Polypody,  258 
Polyporaceae,  230,  345 
Polypores,  232,  345 
Polyporus,  346 
Polysaccharids,  147 
-7**Jolysiphonia,  208,  339 
Polystictus,  346 
Polytrichaceae,  252,  351 
Polytrichum,  351 
Pond  Scums,  178,  333 
Pontederiaceae,  358 
Poppies,  304 
Populus,  304 
Pore  Fungi,  230 
Porphyra,  207,  338 
Portulaca,  364 
Portulacaceae,  364 
Postelsia,  201,  337 
Potamogeton,  357 
Potamogetonaceae,  357 
Potato,  320 
Potentilla,  291,  368 
Pothos,  296,  300 
Pottia,  350 
Pottiaceae,  350 
Powdery  Mildews,  220 
Prasiola,  332 
Prasiolaceae,  332 
Prickly  Fungi,  230,  346 

Pear,  310 
Primary  leaves,  281 
Primrose,  303,  305 
Primula,  303,  304,  323,  365 
Primulaceae,  365 
Primulales,  365 
Prinodontaceae,  351 
Promycelium,  234 
Propagation,  171 
Propolis,  341 
Propyl,  142 
Proteaceae,  372 
Proteins,  87,  150 
Proterandrous,  323 
Proterogynous,  323 
Prothallium.  254 
Protocalamarinceae.  353 
Protocaliciacoae,  341 
Protococcaceae,  332 


402 


INDEX 


Protococcoideao,  171,  332 
Protococcus,  171,  332 
Protomycetaceae,  344 
Protonema,  247 
Protopityeae,  354 
Protoplasm,  1,  151 
Protoplasmic  movements,  110 
Protosiphon,  192,  336 
Prunaceae,  368 
Prunus,  308,  368 
Psalliota,  345 
Pseuclomonas,  331 
Pseudotsuga,  281 
Psilotaceae,  354 
Ptelea,  363 
Pteridium,  259,  353 
Pteridophyta,  254,  352 
Pteridosperm,  272 
Pteridospermalcs,  354 
Pteridospermeae,  272,  354 
Ptilota,  339 
Ptychomniaceae,  351 
Pucoinia,  232,  347 
Puff-balls,  227,  345 
Punicaceae,  309 
Purslane,  320 
Pycnia,  233 
Pycnidia,  239 
Pycniospores,  233 
Pyrenidiaceae,  343 
Pyrenoids,  11 
Pyrenolichenes,  218,  342 
Pyrenomycetales,  218,  343 
Pyrenopsidaceae,  340 
Pyrenothamniaceae,  343 
Pyrenulaceae,  343 
Pyronema,  217,  342 
Pyronemataceae,  342 
Pythiaceae,  335 


Quercus,  310,  311,  372 
Quiinaceae,  363 
Quilhvorts,  258,  352 
Quince,  313 
Quinine,  150 

R 

Radial  bundles,  56 
Radish,  306 
Radishes,  320 


Raffinose,  146 

Rafflesiaceae,  370 

Ragweeds,  375 

Ralfsiaceae,  337 

Ramalina,  216,  340 

Ramularia,  239,  348 

Ranales,  361 

Ranunculaceae,  361 

Ranunculus,  274,  286,  361 

Rapateaceae,  358 

Raphanus,  306,  364 

Raphe,  181 

Raphids,  15 

Ray  flowers,  312 

Razoumofskya,  371 

Receptacles,  246 

Receptacular  cup,  286 

Red  Algae,  205,  338 
-rust,  233 
Seaweeds,  338 
Snow  plant,  172 
-top  Grasses,  359 

Reductase,  153 

Reduction  Division,  111 

Redwoods,  278 

Regular  flowers,  322 

Rejuvenescence,  181 

Relationship,  157 

Reproduction,  109 

Resedaceae,  364 

Respiration,  90 

Resting  spore,  174 

Restionaceae,  358 

Reticulated  veins,  257 
vessels,  36 

Rhabdonema,  334,  339 

Rhacopilaceae,  351 

Rhamnaceae,  371 

Rhamnus,  371 

Rhegmatodontaceae,  351 

Rheum,  365 

Rhipsalis,  370 

Rhizina,  342 

Rhizinaceae,  342 

Rhiziphyllidaceae,  338 

Rhizoids,  244 

Rhizogoniaceae,  350 

Rhizophoraceae,  370 

Rhizopogon,  344 

Rhizopus,  335 

Rhodobacteria,  331 


INDEX 


403 


Rhodochaotaceao,  338 

Rhodochaetales,  338 

Rhododendron,  365 

Rhodonicla,  339 

Rhodomclaccac,  330 
/ilhodophyceae,  205,  338 
'Rhodophyllidaocae,  339 

Rhodophyllip,  339 

Rhodynienia,  339 

Rhodynioniacoae,  339 

Rhodynieniales,  339 

Rhoedales,  3G4 

Rhus,  372 

Rhytisnia,  341 

Ribes,  309.  3G9 

Riccia,  244,  348 

Ricciaccae,  348 

Ricciales,  348 

Riccias,  348 

Rice  Grasses,  359 

Rioinolcic  acid,  143 

Ricinus,  305,  363 

Ringed  vessels,  36 

River- weeds,  357 
^^ividaria,  331 

Kivulariaceae,  165,  331 

Rivularias,  165 

Robinia,  369 

Roccella,  342 

Roccellaccae,  342 

Rockweeds,  201,  337 

Root  (thickened),  320 

Roots,  256 

Rootstocks,  319 

Rosa,  307,  368 

Rosaceae,  368 

Rosales,  368 

Rose,  307,  368 
-apples,  307 

Ronnd  Diatoms,  181,  333 

Rubiaceae,  373 

Rubiales,  373 

Rul)us.  291 

Riulbeckia,  315,  375 

Ruderal  plants,  320 

Runners,  319 

Rushes,  358 

Russian  Thistle,  325 

Russula,  345 

Rusts,  232,  347 

Ruta,  363 


Rutaceae,  363 
Rutilariaceae,  334 

S 

Sabal,  300 
Sabiaceae,  371 
Saccharoniyces,  223,  344 
Saccharomycetaceae,  344 
Saccharose,  17,  146 
Sac-Fungi,  213 
Sachs's  solution,  98 
Sac-spores,  213 
Sage,  304 

Sagittaria,  291,  357 
Salicaceae,  364 
Salicin,  149 
Salicylic  acid,  141 
Salix,  364 
Salsola,  365 
Salvadoraceae,  366 
Salvia,  304,  305,  367 
Salvinia,  259,  353 
Salviniaceae,  353 
Sambucus,  315,  373 
Sand-bur,  325 
Sanguinaria,  364 
Sanicula,  372 
Santalaceae,  371 
Sapindaceae,  371 
Sapindales,  371 
Sapindus,  371 
Saponin, 148 
Sapotaceae,  366 
Saprolcgnia,  186,  335 
Saprolegniaceae,  186,  335 
Saprolegniales,  335 
Sap  wood,  62 
Sarcina,  331 
Sarcoscypha,  224 
Sargassaceae,  337 
Sargasso  Sea,  203 
Sargassum,  202,  337 
Sarraceniaceae,  362 
Sarraceniales,  362 
Saururaceae,  361 
Saxifraga.  369 
Saxifragaceae,  36 
Saxifrages,  369 
Scalariforni  vessels,  36 
Scale  Mosses,  247,  349 


404 


INDEX 


Scapania,  349 
Scenedesmus,  172,  332 
Scheuchzeriaceae,  357 
Schistostegiaceae,  350 
Schizaeaceae,  352 
Schizogoniales,  332 
Schulze's  reagent,  35 
Scirpus,  300,  358 
Sclerenchyma,  32 
Scleroderma,  345 
Sclerodermataceae,  345 
Scleroderniatales,  344 
Scleroderris,  341 
Sclerotinia,  342 
Scotch  Pine,  279 
Scouring-Rush,  264 
Scrophularia,  367 
Scrophulariaceae,  367 
Scrophulariales,  367 
Scytonema,.  165,  331 
Seytonemas,  165 
Scytonemataceae,  165,  331 
Scytopetalaceae,  362 
Sea  Ferns,  192,  336 

Girdle,  201 

Lettuces,  173 

Mosses,  338 

Palm,  201 

Tree,  201 

Umbrellas,  192 
Secondary  leaves,  281 

thickening,  60 
Secotium,  345 
Secretory  cells,  66 
Sedges,  298,  358 
Seed,  271 

distribution,  324 

-ferns,  272,  354 

scale,  278,  279 
Selaginella,  268,  354 
Selaginellaceae,  267 
Selaginellales,  354 
Self  fertilization,  323 
Sematophyllaceae,  351 
Senecio,  376 
Senecionidaceae,  376 
Sennas,  368 
Sepals,  286 
Septoria,  239,  347 
Sequoia,  278,  356 
Seta,  250 


Sexual  cells,  112 

reproduction,  109,  170,  171 
Shade  plants,  320 
Shield-Ferns,  259 
Shoot,  329 

Side  Mosses,  252,  351 
Sieve  tissue,  38 
Sigillaria,  269 
Sigillariaceae,  354 
Silene,  306,  364 
Silicic  acid,  140 
Silks  (of  maize),  298 
Silphium,  375 
Simarubaceae,  363 
Simblum,  345 
Simple  Algae,  170,  332 

pistils,  286 
Sinapis,  364 
Siphonales,  334 
Siphonophyceae,  184,  334 
Sirobasidiaceae,  346 
Sisyrinchium,  360 
Size  of  Cells,  7 
Skeletal  tissue,  46 
Slime  Algae,  163,  330 
Slit-Fungi,  218,  343 

-Lichens,  218,  342 
Smuts,  347 
Snapdragon,  304,  367 
Snowberry,  315 
Snow-on-the-Mountain,  322 
Soft  Red  Seaweeds,  339 
Solanaceae,  366 
Solanin,  148 
Solanum,  366 
Soleniaceae,  334 
Solidago,  376 
Solutes,  81 
Solutions,  81 
Somatic  cells,  112 

division,  112 
Sonneratiaceae,  369 
Sorbinose,  146 
Sorbite,  142 
Sordariaceae,  343 
Soredia,  215 
Sori,  232 
Spadix,  300 
Spanish  needles,  325 
Sparganiaceae,  357 
Spathe,  296 


INDEX 


405 


Spawn.  229 

Special  Adaptations,  319 
Species,  114,  158 
Spermatochnaceae,  337 
SpermoRoncs,  215,  233 
Sperms,  110,  174  . 
Sphacelariaceae,  337 
Sphac'olothcca,  347 
Sphaerobolaceae,  345 
Sphacrobolus,  345 
Sphaerococcaceae,  339 
Sphaeriaceae,  343 
Sphaerioidaceae,  347 
Sphaeroneniclla,  347 
Sphaerophoraceae,  341 
Sphaerophorus,  341 
Sphacroplea,  334 
Sphaeropleaceae,  334 
Sphaeropsidales,  238,  347 
Sphaeropsis,  347 
Sphaerotheca,  225 
Sphagnaceae,  349 
Sphagnales.  251,  349 
Sphagnum,  250,  349 
Sphenophyllaceae,  353 
Sphenophyllales,  353 
Sphenophyllincae,  262,  353 
Sphenophyllum,  262 
Spiderworts,  358 
Spikelet,  297 
Spiraea,  307,  368 
Spiral  vessels,  36 
Spiranthes,  361 
Spiridentaceae,  351 
Spirochaete,  331 
jSpirodela,  358 
^tepirogyra,  178,  333 
bpirogyraceac,  333 
Spirulina,  165 
Splachnaceae,  350 
Splachnidiaceae,  337 
Splachnum,  252,  350 
Spleenworts,  259 
Sponge  tissue,  292 
Spontaneous  Generation,  166 
Sporangium,  190 
Spore-case,  250 

-fruit,  100.  175,  213 

mother-cells.  243 

-prints,  231 
Sporids.  233 


Sporocarp,  175.  213 
Sporochnaceae.  337 
Sporodinia.  197 
Sporogenous  tissues.  211 
Sporophyll.  261 
Sporophyte.  110.  242 
Spot  Fungi.  238,  347 
Spruces,  281 
Squamariaceac.  338 
Squash,  305 
Stachyuraceae,  364 
Stackhousiaceae,  371 
Stalked  Puff-balls,  231 
Stamens,  284 
Staminate,  275 
Stapelia,  322,  367 
Staphyleaceae,  371 
Starch,  13,  85,  147 
Star  Flowers,  370 
Statocysts,  127 
Statoliths,  126 
Stearic  acid.  143 
Stearin.  143 
Stem,  255 
Stemonaceae,  358 
Sterculiaceae.  362 
Stereocaulon.  340 
Stereum.  230.  346 
Sterigmata,  222 
Sterigmatocystis,  348 
Sterile  tissues,  211 
Stickseed,  325 
Sticta,  340 
Stictaceae,  340 
Stictidaceae,  341 
Stictis.  341 
Stigma,  286.  292 
Stigmonose,  134 
Stigonema.  165.  331 
Stigonemataceae,  165,  331 
Stilbaceae,  348 
Stilophoraceac.  337 
Stink-horns.  228.  345 
Stinking  Smut,  237 
Stipules,  292 
Stomata.  51 
Stone  cells.  32 
Stoneworts.  193,  336 
Storage  tissues.  66 
Store  of  food.  319 
Strawberry,  289,  306,  319.  326 


406 


INDEX 


Strcbloncma,  337 

Strelitzia,  360 

Streptococcus,  331 

Striariaccae,  337 

Strigiilaceae,  343 

8trobilophyta,  277,  355 

Strobilus,  273 

Struvoa,  336 

iStryohnino,  150 

Stuartia,  363 

Style,  292 

Stylidiaceae,  373 

Styracaceae,  366 

Stysaniis,  348 

Sub-classes,  160 
-families,  160 
-orders,  160 

Suberin,  155 

Succinic  acid,  141 

Sugar,  145 

Sugars,  17 

Sulphur-bacteria,  169 

Sulphuric  Acid,  139 

Sumachs,  372 

Summary  of  Anthophyta,  315 

Sunflower,  311 

Sunflowers,  375 

Sun  plants,  320 

Super-orders,   160,  361,  365,  366, 

368,  373 
Supply  of  energy,  91 
Supporting  System,  64 
Surirellaceae,  334 
Survival  of  the  fittest,  113 
Susceptibility  to  diseases,  137 
Sweet  Pea,  314 
Symbiosis,  216 
Symphoricarpos,  315 
Symplocaceae,  366 
Symplocarpus,  358 
Synapsis,  111 
Syncephalis,  335 
Synchytriaceae,  172,  332 
Synchytrium,  332 
Synergids,  287 
Syringa,  366 


Tabellariaceae,  334 
Taccaceae,  360 
Tamaricaceae,  364 


Tanacetone,  144 
Tannin.  141 
Tansy  oil,  144 
Taphrina,  341 
Taraxacum,  312,  377 
Tassel,  300 
Taxaceae,  357 
Taxales,  282,  356 
Taxin,  150 

Taxodiaceae,  278,  356 
Taxodium,  278,  356 
Taxodiums,  278,  356 
Taxus,  282,  357 
Tecoma,  367 
Tectona,  367 

Teliosporeae,  213,  232,   346 
Teliospores,  232 
Temperature,  95 
Terfezia,  344 
Terfeziacoae,  344 
Tetrasaccharids,  146 
Tetraspora,  332 
Tetraspores,  206 
Thea,  363 
Theaceae,  363 
Theine,  149 
Thelephora,  346 
Thelcphoraceae,  230,  346 
Thelidium,  342 
Thelocarpon,  340 
Theloschistaceae,  340 
Theloschistes,  216,  340 
Thelotremataceae,  340 
Theobromine,  149 
Theophrastaceae,  365 
Thigmotropism,  127 
Thiobacteria,  331 
Thistle,  324,  376 
Tlioreaceae,  338 
Thorns,  319 
Thread  Lichen,  216 
Thuidium,  351 
Thurniaceac,  358 
Thuya,  356 
Thuyas,  282,  356 
Thuyopsidacoae,  282,  356 
Thymclaeaceae,  371 
Thymus,  367 
Tilia,  362 
Tiliacoao,  362 
Tillandsia,  360 


INDEX 


407 


Till(>tia,  237,  347 
Tillotiaccae,  237,  347 
Tilopteridacoae,  337 
Tilopteridalcs,  337 
Tininiia,  350 
Tininiiaceao,  252,  350 
Tissues,  28 

Tissue  systems,  43,  46 
Toadstools,  229,  345 
Tolypella,  330 
Tolypothrix,  105 
Top  Mosses,  252,  349 
Torreya,  357 
Torula,  348 
Torus,  292 

Touch-me-not,  325,  326,  363 
Tovariaceae,  364 
Toxylon,  362 
Tracheae,  36 
Tracheary  tissue,  35 
Tracheids,  36 
Tradescantia,  358 
Transpiration,  76 
Tree  Ferns,  258,  352 
Mosses,  252,  351 
Trehalose,  146 
Tremandracoae,  363 
Tremella,  340 
Treniellaceae,  346 
Tremellales,  231,  346 
Trentepohlia,  333 
Trentepohliaceae,  333 
Trichocomataceae,  344 
Trichogyne,  174 
Trichomanes,  352 
Trichosphaeria,  343 
Trifolium,  369 
Trinoniaceae,  363 
Trillium,  300 
Tri-methylamine,  153 
Trisaccharids,  140 
Triticeae,  359 
Triticum,  300,  359 
Triuridaceae,  357 
Trochiscia,  332 
Trochodcndraceae,  361 
Tropaeolaceae,  363 
Tropaeolum,  363 
Tropisms,  124 
True  Mosses,  251,  349 
Truffles,  223 


Tryblidiaccae,  341 
Tryblidium,  341 
Trypetheliacoae,  343 
Trypsines,  153 
Tube  Algae,  184.  334 

Fungi,  186,  335 
Tubcraceae,  344 
Tuberales,  223,  344 
Tuber,  344 

Tuberculariaceae,  348 
Tuberculina,  348 
Tuberculosis  bacteria,  169 
Tubers,  320,  344 
Tulasnellaceae,  346 
Tulipa,  358 
Tumble  weeds,  325 
Tumboa,  275,  355 
Tumboaceae,  355 
Turf  Mosses,  252,  349 
Turgor,  73 

movements,  120 
Turneraceae,  363 
Turnips,  320 
Turpentine,  144 

canals,  283 
Tylophoron,  341 
Tylostoma,  231,  345 
Tylostomataceae,  345 
Typha,  357 
Typhaceae,  357 
Typhoid  bacteria,  169 
Typical  flower,  285 

U 

Ulmaceae,  362 
Ulmus,  362 
OLJlothrix,  173,  332 
Ulotrichaceae,  332 
Ulva,  173,  332 
Ulvaceae,  332 
Ulvales,  332 
Umbellales,  372 
l^mbilicaria,  342 
Uncinula,  225,  344 
Union  of  cells,  24 
l^redinaceae,  347 
Uredinales,  232,  347 
Urediniospores,  233 
Uredo.  234,  347 


408 


INDEX 


Uredospores,  233 
Uromyces,  235,  347 
Uropyxis,  347 
Urtica,  362 
Urticaceac,  362 
Usnea,  216,  224,  340 
Usneaceae,  340 
Ustilaginaceae,  347 
Ustilaginales,  235,  347 
Ustilago,  237,  347 


Violet,  302,  363 
Viscum,  371 
Vitaceae,  371 
Vitcx,  367 
Vitis,  371 
Vochysiaccac,  363 
Volvocaceae,  332 
Volvoces,  172 
-^Volvox,  172,  332 


W 


Vaccinium,  365 
Vacuoles,  17 
Valerianaceac,  373 
Valonia,  192,  336 
Valoniaceae,  336 
Valoniales,  336 
Valsa,  343 
Valsaeeae,  343 
Valve,  180 
Vanilla,  361 
Vanillin,  154 
Variations,  112 
Vascular  Bundles,  55 
^aucheria,  185,  334 
vaucheriaceae,  334 
Vaucherioideae,  185,  334 
Vegetable  Kingdom,  159 
Veins,  257 

of  leaves,  60 
Velloziaceae,  360 
Venter,  243 
Veratrine,  150 
Verbascum,  367 
Verbena,  367 
Verbenaceae,  367 
Vernonia,  376 
Vernoniaceae,  376 
Veronica,  367 
Verpa,  342 
Verrucaria,  342 
Vcrrucariaceae,  342 
Vetches,  326 
Viburnum,  373 
Vicia,  369 
Victoria,  364 
Vinca,  367 
Viola,  302,  303,  363 
Violaceae,  363 


Walking-fern,  259 
Walnut,  310,  372 
Water,  71,  139 

Cultures,  97 

Ferns,  259,  353 

Flannel,  185 

-lilies,  364 

Molds,  186,  335 

Net,  172 

Plantain,  289,  357 

pores,  77 
Weberaceae,  351 

Wedge-leaved  Calamites,  262,  353 
Wcisia,  350 
Welv.itschia,  275,  355 
Wheat  Grasses,  359 

rust,  232 

Smut,  237 
White  Pines,  282 

Rusts,  187,  335 
Whorled  leaves,  292 
Wild  Geranium,  302,  326 
Willows,  364 
Wings,  308 
Winteranaceae,  362 
Wood-fibers,  33 
Wood  Mosses,  252,  350 


X 


Xanthium,  375 
Xanthophyll,  11,  155 
Xanthoxylum,  363 
Xerophytes,  320 
Xylaria,  343 
Xylariaceae,  343 
Xylem,  55 
Xyridaceae,  358 


INDEX 


409 


Yeast-Fungi,  344 

Plants,  222 
Yellow  Pines,  282 
Yews,  282,  357 
Yucca,  300,  358 


Zamia,  274,  355 
Zaniiaccae,  355 
Zannichoilia,  357 
Zea,  300.  360 
Zingibcraceae,  360 


Zinnia,  375  ' 
Zonaria,  337 
Zoospores,  171 
Zostera,  357 
Zygnema,  182,  333 
Zygnemataceae,  333 
Zygnema  tales,  333 
Zygogonium,  333 
Zygomorphic,  322 
Zygoniorphy,  309 
Zygophyceae,  177,  33i 
Zygophyllaceao,  363 
Zygospore,  190 
Zygote,  109,  171 
Zymase,  153 


